Monday, October 28, 2013

Repair of the speedometer on a Polaris Sportsman 500 4-wheeler

If you are at this page you probably have a Polaris with a bad speedometer which means that you can't put it in 4 wheel drive and your reverse override doesn't work.
If this has happened to you, you probably ran it without a good battery - or with no battery at all:  Read on to find out why you should never do that if you can help it!
There are at least two versions of speedometers used in the late 1990's and early 2000s - the one that, inside, looks like Figure 4 with "through-hole" components and a slightly newer version that largely uses surface-mount components.  While both versions seem to have the same fate when used with a bad (or no) battery - and the "fix" is likely similar, I have not personally seen the newer surface-mount version, but you can find information on its repair near the bottom of this article as provided by one of the readers.
If you have successfully repaired one of these newer versions and are willing to share the specifics, I'd be happy to post it here.  If you have a "dead" speedometer of the newer version and would likely me to take a crack at fixing it (absolutely no guarantees about success!) then feel free to contact me via comments, below.

Last year, a friend of mine had the battery go bad on his 1999 Polaris Sportsman 500 4-wheeler.  Aside from the inconvenience of having to pull-start it, it seemed to work OK.

Sort of.

Soon, it was noticed that the speedometer had died and interestingly, a few other things quit working at the same time such as the ability to put it into four-wheel drive. When the battery was finally replaced the speedometer still did not work so a he dug around in the internet and found that this is quite a common problem with that vintage of Polaris vehicles - and it seems to work out this way:

The charging system's voltage regulator on these vehicles are fairly simple, but they depend strongly on the presence of the battery to moderate the wildly pulsating DC coming out of the alternator/regulator system to maintain the average voltage in the range of 13.5-14.2 volts or so.  If the battery goes completely bad or is removed, the charging system goes haywire and the voltage can (apparently) exceed 20 volts (and is probably higher) and one can risk burning out the various indicator, marker and headlights.

Another fatality under this conditions seems to be the speedometer module itself!

What (probably) happens:

It's probably not the high voltage that actually kills the speedometer:  The voltage regulator circuit in the speedometer seems to be fairly robust, using high voltage (>=300 volt) transistors to withstand the voltage spikes that are endemic to any vehicle electrical system.  What seems to kill these things is heat.

Let me explain.

The job of the voltage regulator circuit inside the speedometer is to assure that the voltage feeding the circuit inside doesn't exceed about 15 volts or so and from there, it is regulated down even lower by other circuitry for the computer that provides the odometer readings and (probably) the speedometer as well as having something to do with the reverse limiter designed to prevent you from accidentally driving backwards at a high speed and the lockout/controls for the all-wheel drive switch.  There are also several small light bulbs inside the speedometer that provide backlighting for the display at night and these, too, are protected from high voltage by the 15 volt regulator.

Under normal conditions the voltage on the vehicle's electrical system is around 14 volts or so and the regulator's job is to suppress spikes and brief excursions above that and in this mode, the regulator itself isn't doing much.  If the voltage rises, however, it has to drop the excessive voltage and and a natural by-product of this is that it develops heat.

Apparently, quite a bit of it!  In testing the speedometer after the repair I applied 20 volts to it and the main regulator transistor soon got too hot to touch:  If this had been a hot, summer day with the transistor crammed inside the waterproof speedometer casing with no free air ventilation, it would have been much hotter.

So, with the bad battery and a subsequently malfunctioning charging system it is easily likely that the speedometer's regulator saw an average of 20-30 volts on its input.  At some point the transistor overheated and eventually failed internally, shorting itself out.  Fortunately, the majority of the circuits in the speedometer seemed to survive this since once the regulator itself had quit, all power feeding the rest of the circuit was lost completely, preventing further damage.

While a new speedometer is available as a replacement part, it will cost you several hundred dollars, new!

Fortunately, it may be that you can fix it!

The obligatory warnings, etc.
  • Assume from the beginning that the speedometer is a total write-off and that you would have to replace it, anyway.  This way, if you can fix it, you will be money ahead - but if you can't, you haven't lost anything more! 
  • Before you start, read this entire posting so that you'll know what you are in for!
  • Repair of the speedometer requires some knowledge of electronics and board-level electrical components.
  • Repair also requires good unsoldering and soldering skills and equipment - and a soldering "gun" doesn't count.  If you don't have the proper tools and experience in the replacement and installation of individual, through-hole components, do not even attempt this!
  • The speedometer is part of the electrical system of the vehicle and as such, it is possible that its malfunction - possibly due to a failed repair - could cause additional damage to other components.
  • No, I won't repair your speedometer as with shipping, time, "hassle factor" and labor, I'd have to charge a sizable percentage of the cost of a new one.  I suggest that you find someone versed in electronics to help you out if you need to do so.
  • I know ONLY about the speedometers on Polaris Sportsman 500's for the years 1999 and 2000:  If you ask me about speedometers for any other make, year or model, I can't help you!  (They may be the same - they may not - I don't know.) 
  • You do this repair at your own risk!  Do not get mad at me if you blow something up, set fire to your four-wheeler or cause all of your dog's hair to fall out! 
  • Again, there seems to be a (newer?) version of the speedometer with more surface-mount parts that can suffer the same fate.  While I have not seen one of these, personally, one of the readers has provided information about his successful repair:  With his permission, I have posted this update near the end of this article.
  • You have been warned!

How to do it

Remove the speedometer:
The first step is to remove the speedometer from the vehicle.  It's a bit of a pain, but it's not terribly difficult to do as it is almost the same procedure as would be followed for replacing the headlight.

Inside the housing that covers the headlight you'll find two connectors that snap into the speedometer, held in place with release tabs, as well as two nuts that hold the bracket in place:  Note how these go together before taking them off - make a drawing and/or take a picture before you take everything off if you aren't sure.

Open the speedometer:

Place the speedometer face down on a clean, un-cluttered work area on a surface that you don't mind scratching:  It's recommended that you put a rag or old towel between the face of the speedometer and the work surface.

Now, notice the soft, aluminum ring around its perimeter:  This holds the clear, plastic cover to the body of the speedometer by virtue of crimping between those two pieces a rubber gasket.

Wearing leather gloves to prevent being stabbed during this step, use a medium-sized blade screwdriver - preferably one that is somewhat worn out with rounded edges - and slide it between the aluminum ring and the plastic body of the speedometer on the back side, prying the ring open as you go along, straightening it out.  With a bit of practice you can firmly slide the screwdriver along the perimeter and straighten out that soft, aluminum ring and you will probably have to go around several times to do the job.

Figure 1:
The soft, black, aluminum ring around the perimeter of the speedometer that holds the faceplate to the body.  Carefully pry this straight.
(This picture was taken after I'd already opened and repaired it - and partially closed it again.)
Click on the image for a larger version.

Once you get 75-90% of the backside of the ring straightened out, you'll be able to pop the ring off the front:  Set it aside.  With the ring removed you should be able to use your fingernails and pry the front, clear cover from the body of the speedometer.

Be careful with the black plastic rod under the push button, noting carefully how it is installed and taking care that it doesn't fly off somewhere!

Once you have the cover off, set it aside with the black, plastic rod laying inside the cover.

Remove the needle:

This is sort of tricky and it is possible to ruin the speedometer with this step:  Since you have already declared the speedometer to be a total loss, you shouldn't feel too bad if you do.

First, note how far the needle is pushed on to the spindle:  You'll want to remember this when putting it back on.

If you have very strong fingernails, try pulling the needle straight off the speedometer, but whatever you do, apply tensions EVENLY - that is, pull straight out on the needle as you do not want to bend the spindle!  When you pull on the needle make sure that the speedometer is on the workbench with padding on it because if it comes off suddenly, you don't want to slam your hand or the speedometer into the workbench and break something!

If you can't remove the needle with our fingers, you'll need to apply a bit more force.  Cut some pieces of paper or thin cardboard (such as from a cereal box) so that you cover the entire face of the speedometer, but allow access to the needle and its spindle - this being done to prevent you from accidentally marking up the speedometer face.

Now, using two medium-size blade screwdrivers, pry the needle evenly off the spindle using the paper/cardboard to prevent damaging the speedometer face:  You may want to wrap a rag around the body of the speedometer and clamp it gently - but firmly - in a vise.  Hopefully, the needle will come up without breaking anything else!  If you do break something else, save up for a new speedo!

Remove the speedometer module from the body:

Using a small screwdriver blade or, preferably, a similarly-sized and shaped piece of plastic, carefully pry up on the face of the speedometer.  The face is actually printed on a piece of fairly heavy, self-adhesive plastic that is about as thick as a postcard - and it is this, not the actual body of the speedometer itself - that you want to pry up.  It can be a bit tricky to get purchase on the speedometer face and you might bend into a hook a small piece of metal such as a paper clip to act as a tool.

Figure 2:
By carefully prying up the speedometer face's plastic, you can access the three screws that hold the module in the body.  The other two screws are located 1/3rd of the way around, at approximately "10" and "40" MPH.  If you can't get the needle off before this step, make sure that you move it out of the way when you pry up on the face plate so that you don't accidentally break it.
Click on the image for a larger version.

Start by prying up on the plastic face below and in the middle of the LCD odometer display, at the bottom of the speedometer and once you lift it a little bit, you will see underneath it a Philips type screw:  Holding the speedometer face up with a small screwdriver, use another screwdriver to remove that screw.

There are two other screws, each located 1/3rd of the way around on either side:  Remove those, too.

Now, the only thing holding the speedometer module inside the case is friction and the silicone used to seal around the wiring connector pins on the back.  Using a small blade screwdriver, work your way around the perimeter of the inside of the speedometer, wedging gently between the outer body of the speedometer and the module itself, reaching down slightly past the face of the speedometer to do it.  After going around several times, applying a bit of twisting and/or prying force, the module will hopefully break loose and gradually come out.

When it does this, the pins from the electrical connectors on the back will be pulled through the case and soon, you'll have the module separated from the case.

  • There are one or two cylinders with granules packed inside them in the case that contain moisture-absorbing compound.  As you  remove the body of the module, they may come out, or they may be (at least temporarily) stuck in place in their own crevice inside the module - but in any case, note where they originally sit.   Take them out and place them in a "Zip-Lock" (tm) bag and suck out the air to protect them from additional moisture while you are working on the speedometer.

Removing the LCD and accessing the back of the circuit board for soldering:

In order to get access to the "solder" side of the circuit board you'll need to remove the portion with the face plate, after you have removed the needle.  In so-doing, you'll also be removing the LCD odometer display.  It is recommended that you do this over a workbench covered by a rag or towel in case the fragile LCD falls out.

On the back side of the speedometer module (the "component" side of the circuit board) you'll find four black screws that correspond approximately with the four corners of the LCD display.  Laying the speedometer face-down on a piece of cloth, remove these four screws:  The front faceplate portion will separate from the circuit board.

This front portion also retains the LCD in place and it may fall out.  If it doesn't come out on its own, carefully remove it - noting the markings on the LCD and which way they were oriented with respect to the board.

Figure 3:
The repaired board showing the LCD.  Note the orientation of the writing on the LCD with respect to the board.  If you look carefully, you will notice markings on the upper-left edge of the LCD which may be used to indicate which way is up.
 Toward the 2-o'clock position of the speedometer board you can see the repair to the damaged trace.  Because the board is coated with a sticky conformal coating compound used for moisture protection it's difficult to avoid discoloring when soldering due to the heat and flux.   
Click on the image for a larger version.

The LCD's electrical connections to the circuit board are made via two small strips of pink-ish conductive rubber sandwiching darker rubber (often called "Zebra Strips") and these usually stick to the LCD.  If they are stuck to the board, very carefully remove them, but if they are stuck to the LCD, don't worry and leave them in place.  Set the LCD and the rubber strips aside in a clean, dust-free place such as a clean, dry food container.  You may notice that the LCD itself has a part number printed on it:  Note its orientation so that you can reinstall it correctly.

You now have access to both sides of the circuit board.

Identifying the bad components:

Important note (again) about through-hole versus surface-mount versions:

The pictures and descriptions below assume a through-hole version of the speedometer.  It would seem that a later model of this same speedometer uses surface-mount components for some of those that fail.
While I have not seen a surface mount version of this speedometer in person, one of the readers of this blog entry with a failed surface-mount version of the speedometer was sufficiently inspired to attempt a repair - and was successful!
With his kind permission, some details on the repair of a surface-mount version may be found at the bottom of this blog entry.

It seems that the one part that is sure to go is a large-ish power transistor, but there can be two components next to it that are also destroyed - and this damage may be evidenced by some burn marks on the circuit board:  See Figure 4, below, for identification of these components.

Figure 4:
Location of the likely bad part(s).  When I took this picture I had already replaced the TIP48 and the MPSA42 - but not the Zener diode.  There have been reported instances where the parts have gotten so hot that the solder has melted and that they have simply fallen out:  If this is the case with your speedometer, be sure to test the parts before reinstalling them or, if you don't have the facility to do that, simply replace them.
Click on the image for a larger version.

Even though only one or two of these components may be bad, I would recommend replacing all three of them.  These are:
  • A TIP48 high-voltage NPN power transistor.  This is the most likely component to be damaged and is a transistor with a metal tab.  In Figure 4, above, the leads are, left to right, B-C-E.  (The NTE equivalent is the NTE-198.  Note that previously I'd inadvertently listed the '197, which was incorrect.)
  • An MPSA42 high-voltage NPN low-power transistor.  This is a small, black transistor located next to the TIP48.  In Figure 4, the leads are C-B-E from top-to-bottom.  (The NTE equivalent is the NTE-287.)
  • A 1N5245 15 volt, 1/2 watt Zener diode.  This is located next to the MPSA42 transistor and is a small, (usually) red/orange glass device on axial leads.  In Figure 4, the "banded" end is the lower end.  (The NTE equivalent could be the NTE-5024A or its 1-watt version, the NTE-145A.)
The only critical things about the two transistors are the fact that they are NPN devices rated for at least 300 volts to withstand the normal transients found in a vehicle electrical system.  If you are unfamiliar with electronics I would suggest that you replace these with exact types which are readily available from Mouser Electronics or Digi-Key Electronics - or you can get cross-reference equivalents in the NTE family (noted above) from MCM Electronics or even find a local distributor that carries the NTE parts.

If you are familiar with electronic components:
  • The TIP48 may be replaced with about any NPN bipolar transistor found on the "mains" side of an AC-powered switching power supply - such as a dead computer supply.   Typically, these transistors  are rated for more than 400 volts and are in a TO-220 style case - often with a plastic or insulated tab - which really doesn't matter in this application.  Just make sure that it's rated for at least 300 volts and has the same pinout (B-C-E as viewed left-to-right with the leads facing down and the label facing you) as the original TIP48!  Chances are this transistor will have a number that begins with "2SC" (or just "C") followed by 4 digits:  Look up the device's data sheet online and verify that it is, in fact, a high-voltage NPN device.  The one that I happened to used came from a junked VCR, was rated for 500 volts and happened to have a plastic tab rather than the metal tab of the original device.
  • The MPSA42 is a high-voltage, low-power NPN transistor of the type typically used in video drivers for cathode-ray tubes on older TVs and suitable equivalents may be found on the small circuit board attached to the end of a CRT on a discarded television.  I happened to have some ZTX458 transistors - devices that had equal or better voltage/current specs than the original - laying around from another project and used one of them.  Just make sure that you take into account any differences in the pinout of the replacement transistor!
  • I didn't have a 1N5245 1/2 watt, 15 volt Zener around, but I did have a 1N4744 Zener which is a  somewhat beefier 1 watt version with the same voltage rating, so I used it.
Replacing the components: 

  • Unless you are experienced in component replacement and circuit board repair, I would not suggest you do this procedure at all!
  • Use a temperature-controlled soldering iron.  Too little heat, you'll damage the board trying to get the components off.  Too much, you'll damage it that way, as well.
  • Do NOT use a soldering gun for this repair work:  If that's all that you have, you really should not try it as you'll likely ruin the board! 
  • Using your phone or camera, take some close-up pictures of both sides of the board before you start as a possible aid in reassembly.
  • You must have proper desoldering equipment.  A vacuum-operated desoldering tool is the ideal, but "Solder Wick" (tm) or even a spring-loaded "solder sucker" or "desolder bulb" will work.  If you don't have any of these it will be challenging to get the through-holes cleared to install the replacement components without tearing traces off the board. 
  • Both sides of the circuit board and most of the components are covered with a moisture resistant coating.  This coating is slightly rubbery and when soldered, it gets discolored.  Fortunately, you can "solder through" it although extra care should be taken to assure that the solder joints are clean and good.  When you are done soldering, you can clean the flux with alcohol and a cotton swab, but the discoloration will probably remain.  (If your solder uses water-based flux, make absolutely certain that you have removed it using clean water as many of these types of fluxes can slowly corrode connections.)
  • When removing the old components (the two transistors and the Zener diode) it may be easiest to just clip them from the board first using small, sharp diagonal-cut pliers.  This will remove the body of the device and allow each lead to be removed independently. 
Using "solder-wick" or a vacuum desoldering device, remove the two transistors and the Zener Diode, noting the original orientation of each device.  Make sure that you also clean out the holes through the board!

In my case, the heat of the original TIP48's destruction and its subsequent removal from the board actually damaged a trace so I had to repair it with a short piece of wire (I used #30 wire-wrap wire) on the bottom-side (that's the short green wire visible in Figure 3) but it's likely that your damage won't be that severe.

After inspecting for damaged traces, install the new components.  The notes above indicate which lead is which when replacing the two transistors and the diode.

Figure 5:
The newly-repaired speedometer.  It shows a speed because I was injecting a signal on the back to simulate input from a wheel sensor.
If you look carefully you might note that the 10th's of a mile digit on the LCD is missing part of its top half:  To fix it I had to take it apart again, clean the rubber pad ("zebra strip") the circuit board contacts and the LCD with some denatured alcohol and reassemble it to remove the mote of dust that prevented part of that particular digit from working properly.
Click on the image for a larger version.

Putting it back together:

As they say, "Assembly is the reverse of disassembly"!

A few comments:
  • When putting the LCD back in place, it may be a good idea to wipe down the top and bottom edges of the rubber strips with an alcohol-wetted cotton swab, and this should also be done for all surfaces of the LCD itself and the metal contacts on the circuit board.  Doing this will make sure that there aren't any dust particles, fibers or hair that may cause one or more of the LCD's segments to not work.
  • The two rubber strips for the LCD just sit in place, on edge, in the LCD mount and the LCD goes on top of it.  When mating the face of the speedometer back to the circuit board, make sure that you have re-installed the LCD right-side up and oriented properly (remember when you made note of the marks on the LCD?) so that you don't accidentally crush and break it when putting the speedometer face back into place.  Make sure that the four black screws are tightened firmly - but not so tight that you crack the plastic.
  • Before sealing everything up, carefully remove obvious fingerprints from the LCD (using a cotton swab) and the inside of the face plate as well as the speedometer. 
  • If you have a bench-type power supply capable of 12 volts at about 600 milliamps, you can do some preliminary testing of the speedometer by +12 volts to pin "A" and the ground to pin "B".  If all goes well, the lights will turn on and you'll see the odometer displaying numbers.  See below for a description if the pinout.
  • If you have applied power and everything looks OK, gently push the needle partway onto the spindle, aligning it with "0".  With the power applied, move the needle up scale (say, to 20-40 miles-per-hour) and watch it go back down to zero:  If it stops slightly off zero (it may take 10-15 seconds to settle when the unit is powered up) then pull the pointer off and re-align it, re-doing the above steps again until you get it to land on zero.
  • If you can't power up the speedometer, line the pointer up with zero and then move it up-scale to 20 or so.  After 5-10 minutes (yes, it may take that long to slowly move back!) look again to see where it is pointing:  If it isn't at zero, remove and re-align the pointer and try it again.
  • Once you are satisfied that the pointer is correct, firmly push it in on the spindle as far as you noted that it had been pushed before you'd removed it.  Move the needle up-scale by hand again and verify that it will (slowly) move down, indicating that it isn't binding anywhere.  If the pointer isn't pushed in far enough it can jam on the inside of the faceplate.
  • In the case you may have noted one or two small cylinders with granules inside them that are either still in place, or had previously fallen out and it was recommended that they be put in a sealed storage bag.  These are moisture absorbers and they sit in a slight recess one one side of the case.  It is recommended that these be reinstalled
  • When you put the speedometer module back into the case make sure that you move the needle out of the way when you pry up on edges of the speedometer face to reinstall the three screws.
  • Strongly recommended to maintain waterproofing:  Apply a thin layer of silicone grease to the gasket that goes between the body of the speedometer and the clear front plate, taking care not to get it on the face plate where you can see it.  (Just wipe the grease off if you do get it on the display or the back side of the clear cover.)  You may use silicone-based "Plumber's Grease" available at practically any hardware/home improvement store.  Do not use a petroleum-based grease for this!
  • When putting the face plate back on, remember to re-install the black push-rod that operates the button!
  • Test-fit the face plate to make sure that you pushed the needle on far enough and is not rubbing on the inside face plate. 
  • Slide the aluminum ring back into place.  With the speedometer face-down in a cloth (preferably a gap to accommodate the button on the front panel) use a piece of wood to re-crimp the aluminum ring to attach the face plate to the body.  You'll probably have to go around the perimeter several times to get it tight.
  • Squirt a dab of silicone grease (but not silicone seal!) this in each of the electrical connectors on the back side:  This will help prevent ingress of moisture as well as prevent possible corrosion of the electrical connectors.  Again, "Plumber's Grease" or the sort used to lubricate "O" rings is this same sort of grease and will work fine and this is available anywhere you can buy plumbing supplies and parts - including big-box home-improvement stores like "Lowes-Depot."  Remember:  It is not recommended that one use "normal" petroleum grease (e.g. axle grease, Vaseline (tm)) as this will degrade the plastic and connectors!

Comments about pin-out and testing:

Note:  If you do an internet search, you should be able to locate some online drawings showing the pinouts of the speedometer's connectors.  If you do this testing, you would do so before reinstalling it in the case.

With the speedometer facing down, orient it so that the 6 pins of the larger connector are toward the top running horizontally and that the 3 pins of the smaller connector (the one for the wheel sensor) is to the right of it with its pins running vertically.

For the large connector, pin "A" is on the left and they are designated on available drawings as A-F, left-to-right.  For the 3-pin connector they are A-C starting from the top and working down.

Applying voltage to these pins using a regulated, current-limited power supply set to 12-15 volts at a maximum current of 600 milliamps to 1 amp, you should be able to power up the speedometer.
  • Do NOT power the speedometer being tested directly from a battery as that could supply virtually unlimited current in the event of an accidental short or fault.
  • DO NOT connect the polarity backwards - even for an instant.
  • If your current-limited power supply "sees" a dead short, remove power immediately and check for solder bridges around the components that were replaced.

If it works, the lights should come on and if you move the speedometer needle with your finger, up-scale, it should reset itself to zero much more quickly than it had with the power off.  An additional test is that if you increase the voltage above 14-15 volts (but not above 20 volts!) the lights will not get any brighter - a sure sign that the regulator is now working properly.  If you do this, now is the time to double-check that the needle points at zero.

If you are curious, you can apply a square wave signal from an audio generator (3-5 volts RMS) between pins B and C of the 3-pin connector and vary it from about 5 Hz to 200 Hz and you should see the speedometer go up with increasing frequency as you simulate, with your audio generator or "function generator", the input from the wheel sensor.  Pin "C" is ground while pin "B" is the signal input.  The unit must be powered up in order for the speedometer - and odometer, for that matter - to indicate.  If you do not have a piece of test equipment to generate such a signal, a "555" timer chip may be wired up (with the appropriate components) to generate a variable frequency square wave train.

Final words:

If all goes well, your speedometer, 4-wheel drive switch, "reverse override" button and odometer will now work properly again!

Note that there's no guarantee that it will be as waterproof as it was before since you probably lack the special machine required to properly crimp that aluminum ring down so it's probably best to keep it out of rain as much as possible - a good practice, anyway!

Comment:  I occasionally get asked a question via this blog's comment tool.  Unless you include a return email address, you'll have to check back here to see if I've answered it as I won't be able to reply any other way.

As of October, 2015 August 2016 October 2017 November 2018 the repaired speedometer is still working fine.

Repairing the Surface-Mount version of the Speedometer

One of the readers (Mathias) was inspired by this blog entry and decided to attempt a repair of the newer surface-mount version of this same speedometer.  It is not known, exactly, over which model numbers and years this speedometer was in use (or if it still is!)

What follows below details the repair of a unit from a 2000 Polaris Sportsman 335.  Again, unless you are familiar with work on small electronic components and have the appropriate tools to do so, please seek out someone who does have the the familiarity/tools before attempting a repair!  You have been warned!

Figure 6
 Used by permission of Mathias, this is a photograph of the surface-mount version found in a 2000 Polaris Sportsman 335.  It is believed to be (more or less) the same circuitry as that shown in figure 4, above - but using more surface-mount components.
The thread of the related conversation - including a reference to the picture above - may be found in the comments below:  Look for those related to user "Mathias999us".
Click on the image for a larger version.
Figure 6, above, shows the surface-mount version that seems to suffer the same fate when the unit is run without a battery to moderate the voltage.  The above drawing is annotated with some clarifications added below:
  • TIP48 - This is the same power transistor (through-hole) as used in the older version.
  • "SMD marked 1Dt" - This is the same function as the MPSA42 used in the older version, except surface mount.  The case marking of "1Dt" (assuming that the writing was deciphered correctly) is a bit ambiguous, but it refers to an NPN transistor.  It is believed to be a BC846 transistor - a general-purposes NPN device that is rated for 65 volts.
    • It should be noted that the MPSA42 is available in the same SMD footprint as the above and is known as the "PMBTA42".  This may be a better choice than the BC846 in terms of being able to handle voltage spikes, should the Polaris be operated without a battery.
  • "Unidentified diode" - There are two of these:
    • The large one appears to be just a standard diode.  If open/shorted, the surface-mount version of the 1N4003 (through 1N4007) should be fine.
    • The small one is likely a surface-mount version of the Zener diode called out above - namely a 15 volt unit.
  • Capacitors:  These aren't marked in Figure 6, but they are the large, metal cans next to the TIP42.
    • These are often damaged by the heat and voltage when the speedometer is run without a battery.
    • If one/both of these capacitors look at all bulged or swollen, if it looks like their plastic labels have shrunk and split and/or if there is some sort of liquid coming out of them - either from the seam on the top or at the circuit board - they MUST be replaced!  
    • These are reportedly 470uF, 25 volt capacitors.
    • Before removing them note which end of the capacitors are marked with the minus sign so that the new ones may be installed correctly.


This page stolen from


  1. Great informative tips on repairing a Polaris Speedometer.

  2. I have a ? I own a 00 sportsman and was trying to do your fix everything looks exact except some of the electronic parts I have 2 capacitor and a black square block with a pice of metal sticking out of it is what needs to be replaced? I can send pics if u want

  3. As they say, a picture is worth a thousand words, so a photo might be a good idea.

    I really don't have any pictures other than those that appear above, so it may be a bit of a challenge to identify what, exactly, a part might be.

    1. Ordered parts you recommended but once I got into speedo I found the tp48 was correct but the other transistor and diode are surface mount, can I still install them in there place? Also my speedo does light up and did work except the needle part( which I think is speed sensor) now 4 wheeler won't start unless you remove pin "c" black wire from cdi, it will start and run with black wire removed but AWD, and REV OVERIDE won't with black wire removed any help would be appreciated. Thanks for the great post.

    2. Sorry to hear that - I (and, no doubt you!) were hoping for a better result.

      There are at least two voltage regulators in these units: The primary regulator that prevents the voltage from exceeding 13-15 volts, and another regulator for the digital circuitry that is powered from the first.

      If that second regulator is not working - or if it failed such that high voltage was sent to the digital circuitry - the speedometer itself and the computer - which also controls the reverse override, 4WD, etc. - won't work, either.

      I was fortunate in that the second regulator wasn't damaged, but this also meant that I didn't poke around much to determine what components were involved with that second regulator - at least for the "through hole" version: Since I've never laid eyes on the surface mount version I know even less about it.

      Again, thanks for the update.

    3. Very nice directions. Thank you. You have answered all questions before I evean started.

    4. Glad to hear - hopefully you were able to repair your speedometer.

  4. Great write up, thanks for the info. I ordered the parts before I took my speedo apart. My 2001 500 H.O. had different parts. Lucky my TIP41 transistor had just came un-soldered and was laying loose in the speedo. Soldered it back on and its working like a champ.

  5. Thanks for posting this as it was very helpful! I have a 2000 Polaris Sportsman that had similar problems. I pulled it apart and found that the TIP48 was actually lying loose inside the enclosure. Very strange. I bought the ATV used, but there were no indications that any attempt had been made to fix the speedometer. It looked as though the transistor was not fully embedded into the board, and was able to break loose with some vibration. Long story short, I tested the transistor (it was fine) and then resoldered it into board and everything works now. One side note, the 2000 Polaris had a circuit board with more surface mount components. The zener diode and 2nd transistor mentioned above were not easily discerned (but only the dislodged TIP48 seemed to be the problem).

    1. I STRONGLY suspect that the TIP48 got so hot that it unsoldered itself and fell off the board.

      The most likely cause of this would have been a bad battery or flaky battery connection causing the voltage to skyrocket and the device to heat up: It is entirely possible for the device itself to get hot enough to melt solder, yet survive another day.

      Good find, and now that you know what kills the speedo (and the the 4WD switching) on these things!

  6. I saw where you posted you don't repair any, is that still the case? I just purchased a 99 sportsman 500 that had a bad battery and apparently impacted the system. Thanks, Chuck

    1. Hi Chuck,

      Getting into the repair business is not a "can of worms" that I'd care to open at this time, having been involved in this sort of thing before. Chances are, someone you know should be able to help you out - or, perhaps someone that someone you know, knows!

      Best of luck!

  7. Hi KA7OEI,

    Thanks for the awesome write up with great detail and documentation.

    I noticed in of your photos there is a paper document with what looks like to be oem schematic of the speedo with possible pin out. I was wondering if you had some more detailed information that you could post or send me.

    Many thanks

    1. What you see in Figure 5 is a generic wiring diagram for the Polaris, one of which that we found online that shows how things are connected to each other. I don't have a specific link, but it was easily Google-able, as I recall - search "Polaris 500 wiring diagram".

      In the other diagrams are my notes showing how the original transistors are connected, their types, etc.

  8. Mine is a 02. Doesn't have the MPSA or the Zener. The TIP48 is different looking. All solders look great. However my needle turned unusually firmly...having catch in its movement. I cleaned shaft and worked it back and forth. Now it turns much easier. Is the needle suppose to be real easy to turn? There is some rust areas on the outer surface of the ring of the device that the needle actually goes into. Not sure what it is but figure its what makes the needle turn. I thought the needle should turn extra easily the one I took out of my truck did. Any input on this?

    1. The speedometer will have a very small amount of resistance when the needle is moved, but it will move *SLOWLY* back to zero on its own due to the magnetism of the mechanism.

      The "giveaway" that the unit has had a similar electrical failure is that you will NOT have 4WD and that the lights inside the speedo will probably not work: If your 4WD and the lights *are* working, the failure that you are having is probably different.

      I have had a bit of feedback from a few others and apparently the "newer" units use surface-mount parts - that is, more of the parts are flat on the board rather than having their leads sticking through it. Not having seen one of those speedos myself, I really can't offer any specific advice as to what goes wrong with them other than to look for similar-type problems - and, as I saw in one of the pictures sent to me, some "vented" capacitors (e.g. their tops popped open) - probably due to high voltage.

      A few things to remember - at least with Polaris's of this vintage:

      If, at the beginning of the season you find that your Polaris has a dead battery, DO NOT START IT UNTIL YOU PUT A NEW BATTERY IN IT!

      and more importantly,

      NEVER, NEVER RUN A POLARIS 4-wheeler WITHOUT a GOOD battery as it will probably cost you a speedometer AND the ability to go into 4 wheel drive!

      Best of luck!

    2. More of the story. My 4 wheel drive works properly...on and off. The hours meter works properly ,the Speedometer light all work and the odometer works. The only issue was the speedometer itself. Think maybe it was just stuck due to long time storage. I bought it several years ago in many boxes. Speed indicator never worked. I purchased another used one they guy said it worked and it does the same thing as my old one did. I replaced the wheel sensor but it wasn't bad. Didn't think it was because it reads odometer.

    3. That sounds like a different problem - one that is mechanical rather than electrical. If the odometer works and is anywhere in the ballpark, it would expect the wheel sensor to be OK.

      Since you have nothing to lose, check to see if the needle's spindle is cocked at an angle as it may have popped loose from the pivot at the end opposite the needle. If it has, you may be able to put it back in place.

      The other thing to check would be for tiny iron filings between the moving vane (rotor) and the stationary portion of the "motor" comprising the speedometer's indicator - but it may require microsurgery to get access to this. If there *are* filings in there it may be possible to blast them out with very carefully controlled compressed air. (If the unit that you have is at all similar to the one that I worked on, getting that "deep" into the unit may be practically impossible!)

      An "OT" (Old Timer) told me once that the way to remove metal filings fouling a mechanical meter movement (as in a voltmeter) was to use a very brief bit of flame, the idea being that thin iron filings would burn more easily than the meter's parts: I've tried this several times with nothing to lose and managed NOT to completely ruin the meter (which would have already been a lost cause) and make these filings go away only once...

      It could also be that the pivot(s) are "dry" of lubrication: About the only thing that one could use there would be very fine watch oil or some sort of Teflon-based lubricant as anything thicker than that would probably have too much drag.

      Best of luck!

    4. I tried the needle setting process without bench power. My needle never moves back toward O.

    5. Right as rain on that powered bench test. Needle wouldn't move toward O at all without power but when I did the bench power test... lights worked great and when I moved the needle to 20 it returned right away to the O. Any quick way to do the audio Audio HZ test? I don't have a device to do that I don't think.

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    7. The only way that I can think of simulating a wheel sensor using things on-hand other than an audio signal generator would be to use a PC/laptop (running Windows) to generate an audio signal with a free program like "Audacity" - say, several minutes of a 100 Hz tone.

      Playing it back on a computer, feeding it into a cheap set of powered computer speakers, take the output of the computer speaker connector, disconnecting the speaker. Connecting one side (the shell of the connector going to the speaker) to ground and the inner pin to that which would go to the wheel sensor and then *slowly* increase the volume on the powered computer speaker until it registers on the speedo. The "speed" would be proportional to the pitch of the tone.

      If you don't feel completely comfortable doing this, just plug it back into the Polaris, wires hanging everywhere, and carefully drive around!

      I'm guessing that, perhaps, the newer speedos "lock" the pointer when the power is off - like the dashboard gauges of many cars these days?

    8. I got the audio signal from U tube. Rigged the speaker and tested it all. Hooked it to the speedometer and got nothing. Does the speedometer need to be hooked to the bench power while I test the audio for speedometer movement?

    9. Yes, the speedometer does need power for the electronics for it to indicate. Both the speedometer should go up and the odometer should (slowly!) increment.

    10. I think I messed up. Still got nothing to happen.......but I had it all hooked up and had the audio going and turned the speedometer so I could see the face..the lights went out. I must have got a short in a connection. Now when I do the normal bench power test the needle does not return to O and I feel no resistance to it. The hour meter still works they will change as time permits and the lights still work. I'll try again later but suspecting the worse at this time.

    11. I was wrong. I cracked the shaft of the dial. If someone does that a might cure is... use a small piece of 18ga shrink wrap. Put it on the shaft and use a match so as not to get too much heat. It worked on mine.

  9. The speedo on my 2001 Sportsman 500 went bad and was replaced. Does it need to be calibrated for speed? It seems to read higher than actual speed.

    1. The speedometer/odometer works by counting the rate of pulses from the wheel sensor - there's a computer in the speedo that does this to calculate the speed and distance traveled.

      The ways that a speedo could differ from an old one would be:

      - The old (or new) one is bad
      - Different model/type/manufacturer
      - Something wrong with the wheel sensor (more pulses = faster)
      - Tire different size (smaller = faster)

      I looked to see if there could be a way to calibrate the units for speed, to compensate for different tire sizes, but Google hasn't revealed it - sorry.

  10. On the opposite side from the parts you replaced is a round black piece with a flat side. In the middle of it is a white piece that looks like it could turn with a philips screwdriver. Do you know what it does? I think it is used to calibrate the speedometer but not sure. My dial does not move. This piece has rust on it. Wondering if it might be the problem. This is a different one yet exactly like it. I got it on ebay and I was told it works properly. When I got it installed the speed indicator does not work. The exact pieces that you originally talked about are just like my old one and different than yours. Needle turns easily and the front has been removed before. Doesn't look like anything has been messed with. I opened a claim but for some reason they said he properly listed the item and ruled in favor of him. Odomer, trip, mileage, hours and lights all work and 4x4 turns on and off. Any thought?

    1. Being that the speedo was on my friend's '500 - and that I fixed it as shown in the pictures - I don't have it to look at anymore, except in the pictures.

      I've sort of lost track in what parts and pieces that you have laying around, but you may be able to transplant some bits and pieces between the two and make one working unit, provided that wire locations are very carefully noted as you disassemble, taking pictures and more importantly, notes.

      Since the needle on the Ebay unit reportedly moves you may be able to "marry" the two units together - just be VERY careful of the fine wires. Just make sure that you use a soldering iron and not a soldering gun and be sure that your soldering skills are up to snuff - or find someone whose are.

      Best of luck!

  11. When looking at your picture... the Zener diode has a bit of rust color on the bottom end covering the actual solder. Is this a indication of a bad diode?

    1. In the picture, the "bad" part had no visual indication of there being anything wrong with it.

      Diodes (in general) have a "band" on one end indicating the anode connection - important since they are polarity-sensitive devices: This band coincides with the "line" end of the diode symbol (e.g. a triangle pointing at a line.)

      A bad diode can usually be detected by using the "diode" function of a volt-ohm meter (some of the cheap Harbor Freight meters even have this!) and verifying that there is conductivity (500-700 millivolts) in only ONE direction.

      Properly checking a Zener diode is trickier since they will test as a diode in one direction, but they are supposed to "break down" at a specified voltage in the opposite: If exposed to excess current, they can still check out as diodes, but their "Zener" voltage can drift - and this could only be properly tested using a simple test fixture (resistor, Zener in series).

      If there is any doubt at all, simply replace the Zener!

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  13. Hello, thank you for all the information you have provided. I did the suggested repairs and when I placed my 1999 polaris sportsman 500 speedometer back in, it worked as it should. However after about five cycles of the key off and on, I noticed the lights dimming and the LCD went blank. Would you have and advice or information as to why this may have occurred? I plan to pull the speedo back out and possible do the repairs again?

    1. It sounds as though the regulator components that you replaced failed - perhaps not all of them (the two transistors and the Zener) were replaced and/or installed correctly: Make sure to compare the pin-out of the replacement device with the new one. It is also possible that there is a high-voltage transient that killed a component - one of the reasons that I think that the original parts were rated for such high voltages.

      Others have reported that sometimes the large capacitors on the board are damaged when the regulator fails. Sometimes this is obvious (bulging, leaking, etc.) but not necessarily.

      If you are careful you should be able to connect the speedo without putting it in the case, but while the pins/connectors will fit (after a fashion) one will have to make sure that things are connected the right way-round (if they aren't keyed by a missing pin) and that nothing shorts out to the chassis of the '500. In that way you could see what gets hot before putting things back together.

      Best of luck!

  14. Hi there I loved this article. EXTREMELY informative.

    I took everything apart as listed. And there is no visible burn marks or damage... The three lights
    In the speedo come on but are very dim...even when hooked up to the atv. Also,the needle returns to 0. Still no lcd or overdrive or AWD? Could it be something else any thoughts?


    1. First check the supply voltage to the speedo: It should be pretty much that of the battery.

      If that is OK and if the lights are *VERY* dim, check the voltage on each of the three leads of the large transistor mentioned (the TIP48 or whatever it is) against ground. The voltage should be no more than 2-3 volts below the supply voltage to the speedo. If it is *way* below the voltage, one or more of the parts mentioned in the posting may be damaged - particularly the Zener. It could also be that one of the large capacitors is damaged as well - especially if it shows any signs at all of swelling/bulging.

      Best of luck!

  15. Thank you for your very in-depth article. I have a 2001 400 with speedo/lights/and 4wd inoperative. I took apart the speedo as suggested and found both capacitors with obvious visual failures. I did run this with bad and no battery. Would changing just the caps fix my issues? Seems nobody does any electronic repair any more in town to ask any help or advise from. When looking for replacement caps Mine say 25v 470 micro farad CKRM M85 C what is CKRM?But when I go to digikey there are other specs like ripple current and series that I am unsure of?Any info would help. Thanks again James

    1. Hi James,

      On a hunch I Googled "CKRM" and found that it refers to a product line of Cornell Dublier/Illinois Miniature Capacitor.

      Of the specs that you'd mentioned that are most important the capacitance and voltage (470 uF, or microFarads, 25 Volts), and a capacitor of equal or higher voltage (at the same or higher capacitance) will be fine. The "85C" refers to the temperature rating.

      In perusing Digi-Key, I would recommend the following:

      - Pick a capacitor with the same ratings: 470uF, 25 Volts
      - Find one with the same lead spacing (center-to-center) so that it will fit into the same holes.
      - Make sure that its body diameter and height is equal to or smaller.
      - Pick one with a "105C" temperature rating.
      - If you can find one in the family labeled "Low ESR" and/or described as being for switching supplies (also rated for 105C) with the same sizes, etc. the by all means use it: These are very slightly more expensive but much higher quality and more rugged. For this application thinks like ripple current and ESR is not particularly important. (Practically speaking, I'd bet that you could put almost *any* 25V, 470uF capacitor in the location and it would be OK - but since you are ordering parts, you might as well get something reasonably good...)

      If you are really lucky, the voltage, by greatly exceeding 25 volts and popping the capacitors, has protected the other circuitry: While you could use a higher voltage capacitor (35, 50 volt) with the same or slightly higher capacitance (as long as it would fit in the space on the board!) the lower voltage rating of the capacitor and its higher likelihood to blow up in the event of a malfunction could be protective... in theory.

      Then again, I would not be surprised if you were to look at 1000 different 'speedo units and find different manufacturers', types and voltage ratings, etc. in there!

      Best of luck - and let us know how it works out.

  16. Hm? I posted a comment and it did not show up. Maybe you have to approve it first perhaps. In any case, let me try again and feel free to delete if both eventually show.

    I also have a 99 500 and followed your instructions to the letter. However, when I opened my speedo up, the board seems slightly different than what you have pictured in figure 4. Mine does not have the MPS44 low transistor nor the zener diode as you pic. I have a pic of mine to show you, but do not see a way to upload here. Maybe I can e-mail it to you for comparison. My e-mail is:

    Everything else is 100% matching to what your Figure 4 circuit board looks like except the 2 items you mention replacing. I did find that the 48TIP transistor was not even connected to my board and just flopping around loose. I was hoping for an easy fix, so cleaned the 3 solder holes and soldered the 48TIP transistor back in place. Connected the the ATV plug ensuring correct pin orientation and nothing. The back-lighting bulbs didn't even light up and the bulbs do not appear blown. If there is a way to get a pic to you, maybe you can give it a second look and see if I'm missing something?

    1. There have been other reports of parts having been found loose in the 'speedo housing, clearly due to overheating to the point where the solder has melted. In at least one case noted in the comments above a repair made by soldering it back into place was successful - but that is likely a matter of luck!

      You may have the version with surface-mount components, which does include the Zener and smaller transistor. Unfortunately, I've never seen one of those in person, or else I would have documented a repair for it.

      As for pictures, people have attached them to their comments here and I have received them, so I'd try that route first.

  17. Yeah, I was hoping I'd be so lucky as to just solder it back in, but not my're probably correct on the surface mounted pieces. I've got some 48TIP's on order now and hopefully those will take care of it. I'm not sure how anyone was adding attachments to their comments as I don't see an option to do so. No biggy, sounds like you answered my question enough to explain why mine didn't look 100% as yours did. I'll update once I get the new transistors in the mail and installed. Wish me luck! I appreciate the quick response and very thorough "How To" guide for the repair overall.

    1. From what I can tell the circuits are similar, so there should be a surface-mount Zener and an *equivalent* of the MPSA42 on the board - likely very near the location of the TIP42.

      Best of luck, and let us know how it works out.

    2. Received mt TIP48's in today. I replaced them both, but no fix. Looks like I have my usual "worst luck." I did check eBay again today and got a NIB for $300 instead of $400, so I suppose that's my silver lining.

      Again, great write-up my friend and I thank you for taking time to put this together.

    3. Sorry that the repair wasn't that simple: I hope that you find a good deal on one!

      It might be interesting to get my hands on a "dead" one of the version that you to see what I find - you never know!

  18. I have a speedo apart and the only visual damage is to a phier Spain component, which is at the top right of the board, 3 prong with a white center, do u know the specs on that so I know which to order, I belive the numbers on the side of the component says 33 18

    1. Unfortunately I don't have that part included in my pictures on the web page and I don't have a "dead" or disassembled speedo to look at for analysis.

      This sounds very much like a small potentiometer - possibly for speed calibration or the like, but the numbers "33 18" don't make sense. I would expect something like "1k" or "50k" (e.g. 1-3 numbers followed by the letter "k" or, less likely some numbers in front of "M") or just three numbers together - this indicating the resistance value of the potentiometer.

      Best of luck!

  19. I have those 3 pieces on order and went ahead and disassembled my speedometer. Only burn marks I found is on one thing. Not sure on how to order it cause of no numbers or letters. Here are pics.




    1. I don't see anything that is obviously "smoked" in the pictures.

      That is, however, one of the "surface mount" versions of the speedo - which I have never seen in person (see other article comments) so if you are successful in your repair, please let me know.

  20. Would cleaning the zebra strip help with a very dim LCD. Its so dim i need a magnifying glass to read it!

    1. When the Zebra strip goes flaky, one usually sees that there are certain - but not all - segments/portions of the display that are affected. In other words, certain segments may be missing/faint while others appear normal.

      Having said that, it may be that it will help - but I kind of doubt it. If the unit has been stored outside in the sun without a cover, it may have been degraded by a combination of the sun and heat.

      Finally, it may be that the voltage regulator for the computer circuitry may be have a low voltage, but just high enough to still be functional such as what can happen when an LCD digital clock/watch has a weak battery. If you have ever run the unit with either no battery or a bad battery, one or both of the regulators (e.g. the one described in the "fix" on this page - and yet another regulator dedicated just to the speedo's computer) may be damaged/failing.

      Best of luck!

  21. Thank you for a well written article! I especially like the realistic detail like using cardboard from a cereal box. You write just like I think and that makes this article a good read.

    1. Thank you for the comments - and I hope that you and others find the article useful!

  22. I replaced the 3 parts plus the 470uf cap (near the edge) as it was obviously cooked. Now, when I power up, I get dim lights, no LCD display, and within 30 seconds or so the TIP48 was hot enough to burn my finger.

    The board was burned under the MPSA42. Any thoughts on what else to test/replace? Thanks for a great article.

    1. With the heating of the TIP48 one can presume that excess current is being drawn. A careful examination of the circuit board is warranted to determine if any of the traces are compromised, or if there are any inadvertent solder bridges/shorts on the bottom side.

      With the board underneath the MPSA42 being damaged I'd look for the cause - possibly due to the '42 itself, or the Zener nearby being cooked: Both should be checked - probably replaced as they are inexpensive enough. I'd also verify that all of the large electrolytic capacitors involved are OK as excess heat could cause them to become very leaky or even short out - and, of course, make sure that their polarity is correct upon installation.

      If no fault is found, additional components to check are the several diode nearby: In general, an ohmmeter to determine if they are shorted out (a few Ohms or 10s of ohms) will suffice.

      Somewhere on that board will be another regulator, taking the 12-14 volts being output by the TIP48/MPSA42 regulator circuit and reducing it to a still-lower voltage (probably 5 volts) to run the computer/display portion - possibly a device marked "7805" or "78L05" - that should be investigated as well.

      Finally, it would be interesting to see if any component other than the TIP48 is getting warm, indicating that it, too was shorted out.

      Fortunately/unfortunately, I don't have access to the speedometer in the pictures anymore - mostly because it has been repaired and is back in the 4-wheeler so I don't have one on-hand to examine. In retrospect, I should have taken more pictures and notes while I had it on the workbench, but c'est la vie.

      I'll be interested in knowing what you find. Best of luck!

  23. I have the "newer" speedometer board. Its all surface mount. Before I dig deeper and ruin something..Have a question.
    With 12 vdc applied, I have back lighting and LCD numbers displayed. I have no square wave generator. I jacked the RF wheel off the ground and spun it manually. I had no indication of pointer movement. And no, when I drive it there is no speed indication. Glass is so etched up I could not see if digits changing or not. Your thoughts from here?

    1. It would be interesting to note if it will go into/out of 4WD and/or the reverse override works: Both of these functions are (I believe) under control of the computer within the speedometer unit.

      Whether or not it's the very same circuit that does the 4WD/REV as does the odometer, I can't say - but they do share the same power supply circuitry - but if one function works it's reasonable to believe that this power supply function is OK.

      If the other functions work and there is no odometer/speedo indication, I'd re-check the connections to the wheel sensor, making sure that they are plugged in, not corroded: If another speedo can be borrowed, swap and see if the problems track the unit, or the vehicle (e.g. sensor).

      Best of luck!

  24. First off, thanks for the excellent write up, it's appreciated and helpful. There is one question I hope you could answer regarding the LCD. As I was almost finished with the repair, the LCD fell off including the clear plastic piece that holds the LCD and Zebra Strips to the circuit board. A little metal contact fell out that sits underneath the clear plastic holder. It looks like there should be one on each side, but I only found one. Not sure if one bounced away or if there is only supposed to be one. It certainly looks like there should be a contact on each side. Any ideas? Thanks in advance! Ron

    1. Since it's been about 5 years since I wrote this article, I don't recall specific details of the small pieces - but the "metal contact" that you mention wouldn't actually be a contact (the Zebra strip does that) but more likely a guide or a mechanical stiffener.

      If you can't find another piece (say, with a magnet) then put it together "provisionally" (e.g. don't crimp the ring back together just yet) and try it.

      As noted in the article, even the slightest mote of dust on the Zebra strip will make the LCD flaky with some missing segments, hence the cotton swabs and keeping dust and strands away from the zebra strip, the back of the LCD and the contacts on the circuit board.

      Best of luck and thanks for the note!

  25. Hello. I have the same speedometer that you fixed. My Polaris 2000 was without batery about 1 year. My speedometer works everyrhing, backlights and hours digital counter, only the speed counter and the digital miles counter doesnt work. Do you think is the same problem you had? or could be the speed sensor? Do you know how i can see if the speed sensor is good or bad?
    Thanks for the help

    1. If your battery was ever dead/removed and you ran the engine, you likely damaged something. It would be interesting to know if your reverse override works or if you can put it into/take it out of 4WD.

      If everything else works, it may be that something with the digital display has died - perhaps you can recover it by cleaning the "zebra strip" mentioned in the article and re-installing the LCD glass, but if that's all that wrong, I'd probably leave it alone.

  26. Hi, Thanks for your most excellent, detailed writeup of this procedure. I too have a dead speedometer from a 2000 Sportsman 335. Upon opening, I discovered that it is the surface mount version. The TIP48 is through-hole, but the diode and MPSA42 have been
    replaced with SMDs. I have a closeup pic with callouts here:

    Applying 12VDC to pins A (+) and B (-) produces no output from the speedometer whatsoever. No lights, no needle movement, nothing. Before thinking, I removed the TIP48 from the board, but then tested it using both diode test feature and transistor test feature on my DMM, and I believe the TIP48 is functioning as desired. I was able to solder it back in place successfully. As you can see, there are two SMD diodes and a SMD transistor in the area where your through-hole diode and MPSA42 were. I tested the diodes in-place on the board, and believe them to be funcioning. I can't quite make out their markings with my loupe. The transistor on the other hand is marked 1DT. After looking up a cross-reference chart, I believe this is a BC846 SOT23 general purpose NPN transistor rated for 65V, and is the "replacement" for the MPSA42 transistor. Using the diode test feature on my DMM on this device while in place on the board, all I get is open circuits (actually the B-to-C and B-to-E tests give a transient drop reading which quickly climbs to open circuit within a second). I believe this device is defective, and that makes since, because the TIP48 is rated for a much higher voltage (300V), and the original MPSA42 is also rated for 300V, while the "new" BC846 is the weak link at 65V limit. Link to a datasheet:

    I can't quite discern what the role of this smaller transistor is in the circuit. Would I expect ANYTHING to function if this transistor is faulty? (e.g. lights would still work?). I have a decent soldering and hot-air rework station and could potentially attempt the repair. I'd have to source the replacement part, and I'll openly admit that this is right at the limit of my soldering skills.... I guess it's junk anyway, and worth a shot.

    Either way, hopefully this info will help someone else get further in repairing the surface mount version.

    1. I believe that the two transistors work together as a voltage regulator, along with a Zener diode, very likely one of the two "unknown diodes" that you marked. Depending on the circuit topology, it may be that the smaller transistor need not be required to withstand the full voltage.

      Presumably, the circuit is similar to the through-hole version which means that the Zener is likely a 12-15 volt unit.

      One should get the "two diodes" when checking a transistor so you are probably correct in presuming it to be bad: The climbing reading you get is also likely due to a capacitor in the circuit.

      The Zener would test as a "normal" diode with a meter - one would have to use a curve tracer or construct a simple shunt-regulator circuit to verify it - but since Zeners usually seem to fail shorted, it's probably OK.

      Finally, I would not expect anything to work without the regulator - not even the lights, particularly if they are incandescent.

      I'd be interested in your results, successful or not.

    2. Hi Clint, Thanks for your followup and confirming my suspicious. I can now add a few more facts to the discussion. I decided to attempt to unsolder the old SMD transistor before ordering a new one (as my surface-mount soldering skills are quite green). When I grabbed the device with my tweezers, the case crumbled before I ever applied heat, clear evidence of thermal damage. I used the hot air rework gun and the device came off with minimal fuss, and the solder pads on the board look clean, undamaged, and usable. I managed to snap a pic of the damaged device through my loupe after it was removed:

      I think you can clearly see that the transistor casing is brittle and sustained thermal damage, so I think I'm on the right path. Also, performing the diode tests on it after it was removed revealed all open circuits, and a diode test on the solder pads on the board still reproduced the climbing reading. So, I think the transistor was indeed dead, and the rising reading was indeed due to a capacitor which remains on the board, as you suggested.

      Given this minor success, I've been spurred along with the confidence to order a replacement. I found what I believe to be the exact part on digikey, and I ordered 5 of them at a whopping $0.14 apiece to account for my aforementioned SMD soldering skills. And paid 5X that in shipping costs. I'll report back with the outcome and any other details when the parts arrive and I attempt the repair. Thanks again for your help.

    3. Thanks for the follow-up - and I'll be interested in either your success or failure!

      An interesting quirk about DigiKey is that if you send them a check or money order in snail mail, shipping is free - at least for small orders - something to remember if you need a small number of parts, but aren't in any sort of hurry! (This is mentioned in item 6 of their "Terms and Conditions".)

    4. Hi Clint,

      Well, I didn't even pay attention to where DigiKey is located, and I was surprised to see the parts arrive in my mail today. Turns out they are only a few hours drive from where I live, so the cheapest shipping was as good as overnight.

      I carefully soldered one of the new surface mount transistors in place, applied 12V to the power pins and...

      IT WORKED! Everything is functioning on it. Apparently this machine had 391.1 hours on it when the speedo stopped functioning. Who knows when that was, given that it is nearly 20 years old. I bought it used just this past summer, fully aware that the speedometer was not working. I have already applied the 4WD switch bypass to the wiring harness, which I will now undo. Fortunately I left the leads long with an eye towards hopefully reversing that mod one day (which is now going to be a day in the not-too-distant future).

      I used this project as an excuse to get an entry-level oscilloscope and signal generator in kit a few weeks ago. I used the signal generator on the B and C pins for the wheel sensor, and the needle indicator is working perfectly. I get full deflection to 60MPH reading at around 320Hz.

      In case anyone is interested, the DigiKey part I ordered is 1727-4851-1-ND mfr part # BC846,215 and can be found at this URL as of this writing:

      To commenter Ron Stier on October 6, 2018 above. He probably figured this out already if his was ever reassembled, but the little metal contact is actually the detent / contact plate for the switch for changing the LCD function with the pushrod. I too was hunting around for a second one after I took it apart because the bracket and contacts on the board can accept one on each side. There is only one, and it must go on the left side as you look at the front of the speedometer in its normal orientation.

      Thanks agqain for your help Clint! I think this one repair project easily paid for my soldering/rework station, hobby grade oscilloscope and function generator. Probably and then some. Couldn't have done it without you.

      As an aside, I made a serious study last spring for my radio license. I was almost ready to go get my technician, general, and extra in one sitting when I got sidetracked with other things in life. If I ever get back to that and complete it, and get a radio setup, I'll have to try to make an interstate contact.


    5. Kewl on the successful repair!

      With your permission, I would like to add the information about the SMD version to the above so that they are all in the same place.

      BTW, did you ever figure out which of the diodes was the Zener? If its the Zener, it would likely be connected directly to the base of one of the two transistors: Since I found the Zener in the unit that I'd repaired to be fried, it would probably be a good idea to know what goes where.

      Again, congratulations - and a project like that is always a good excuse to by new (and useful!) toys for the workbench!

  27. I have the same speedo as Mathias but the only part that looks bad on mine is a black rectangle box at the top. I have 2 good pics but dont know how to post on here

    1. Update, its the cs421 and it controls/converts the signal from the speed sensor into mph.

  28. I have a 2000 sportsman 500 I bought knowing the speedo didn't work but everything else works fine I have to wiggle the 4wd switch sometimes but it works as well as the reverse over ride. nothing on the speedo works no lights no odo no speed and also I am no electrical wiz so my question is could it be something other then the internals on the speedo making it not work

    1. If you have *EVER* run the machine without a good battery connected (that is, a completely dead/ruined battery or no battery at all) the speedometer was probably damaged: This is what usually happens.

      If you are pretty sure that this has NOT happened, you can cross your fingers and hope that a connector has come off and/or a wiring harness has been damaged.

      The best bet - if you can - would be to temporarily try another speedometer (making sure that the battery and charging system is working so you don't blow that one up) and see if it works better.

      Best of luck!



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