Colin,
you may not need to change the speedo, below I haved copied a DIY one of our friends across the pond did. May be it'll work for you.
PROBLEM:
Your speedometer works, your odometer quit. Chances are, your drive gear has given up. The popular story is that you hit the trip meter reset while the car was in motion. While it is entirely possible that
that particular event was the event that caused the actual failure, the root cause lies at the VDO factory. The tiny, little, 15 tooth planetary gear that drives the odometer and trip meter from the speedo sensor has turned into a soft jello like rubber over the years due to excessive heat and a corrosive oil lubricant that has turned that essential gear into mush. The separation of a couple teeth from that gear has been inevitable.
Your repair choices consist of sending it to a reputable speedo shop and dump a couple hundred bucks into a rebuild and be sans speedo for at least a week, or give it a run yourself. Replacing the gear is
NOT that difficult. No crazy tools are needed. No special skills are needed. But it is risky. The most finnicky point of the rebuild is dealing with removal and reinstall of the needle pointer onto its shaft. The shaft of the needle is tiny... very tiny. Break that and you are looking at replacing your speedo. These aren't cheap speedo's... the broken gear is.
NOTICE: This DIY procedure will
NOT help you change the mileage on your odometer. The main assembly holding the numerical wheels in place is not easily opened. You will not be able to roll your odometer forward OR back. Trust me... I tried. I wanted to add a bunch of miles to get back to reality, but there is no easy way to get the numbers free wheeling. Furthermore, tampering with the mileage on your odometer is illegal... or something like that.
Anyway, I did this on my first attempt with relative ease and great success. Your results may vary. Don't attempt at home... unless you are willing to accept the risk of ruining your gauge.
STEP 1: Odometer Removal.
Using a cloth covered screwdriver, gently pry the speedometer out from your dashboard. The rubber ring around the edge comes out too so get under that with the flat screwdriver and pry out. Do NOT use the neighboring gauge as a leverage point. The black trim ring is very easily scratched. Once you get it started you should be able to get your hands on it and pull it out. Unplug the connector and head to a clean work area.
STEP 2: Disassembly
TRIM RING: Remove the rubber grippy retainer ring. Remove the 4 screws from the back of the unit.
Now the soft metal trim ring needs removed by gently prying around the entire edge of the assembly to bend/lift the edge over the lip of the outside housing. This isn't pretty, but go slow. Be careful not to scratch the ring beyond the lip. You won't see what you have done to it once the rubber retainer goes back on so don't worry about chewing it up a little bit. Keep slowly prying around the edge until it can be pulled out.
STEP 3: Trip meter reset button removal
There is a thick post over the thin post of the reset button. Support the button assembly below and pull the top off. This will take some pressure, but be sure to brace the assembly from below so you don't pull too hard on the lever where it clips to the drive gears.
Note where the shaft gets thinner... that is where it separates.
STEP 4: Speedometer needle removal
This is the trickiest part of the job. The needle is pressed onto a shaft that is extremely thin. It feels like a pretty tough metal, but you HAVE to be careful here. Do not pull straight up. Do not put any torque on the shaft. Rotate the speedometer needle clockwise until it hits a stop point. Gently continue to rotate the needle whil lifting up gently at the same time. The friction is all that is holding the needle to the shaft. Keep turning and prying until the needle comes off. Do not force it. I don't know that that shaft assembly is user replaceable.
Note: See how small the shaft is:
STEP 5: Disassembly
You've come this far, there is nothing stopping you now. Take the two screws out of the faceplate.
Remove the circuit board.
Remove the motor.
STEP 6: The guts
Once the motor comes out, you will get to the drive gear and pod. Inside the pod is going to be your broken gear. Replace it with your new gear.
See the broken gear - and its yellow decay - compared to the new gear.
STEP 7: Reassembly
This is completely reverse of everything else. Nothing is too tricky. Continue to take your time paying particular attention to the needle shaft. When reinstalling the speedo needle, make sure you rotate while gently pushing down. Never simply compress the needle onto the shaft. Once it is in firm enough, use the stop points at max speed and 0 mph/kph to realign the needle with 0. Once everything is back together, also gently recompress the trim ring around the back of the speedo housing. You could use a black permanent marker to cover any scratches. Plug the unit back into the dash and reinsert into your gauge opening. Hopefully all is now re-recording miles.
PARTS and BACKGROUND INFO:
The new gear cost me $25 as of this writing in June, 2005. I found the gear at
http://www.odometergears.com/. Jeff Caplan at Odometer Gears is a top notch, class act. I called there looking for help in isolating the part and he gave me spot on directions on how to get into the speedo, what to watch out for, and what to do once in there. Once I got things figured out, he had a new part in the mail that same day. You can call him at 757-593-3478 or email him at
order@odometergears.com. My car is a '95 993 but I think all 964's, 968's and 993's will use the same 15 pin gear found when you hit the "Porsche" link at their website at
http://www.odometergears.com/. Check with him first if you aren't sure.
Again, this is a
VERY easy job. Not easy like a tire change - but only because you are dealing with a delicate instrument. If you have big, clumsy hands, you might want to forego this exercise and send it to a pro. If you can be gentle with this, you should be ok.
I hope this is helpful. I'll be sending this along to p-car.com soon. Please let me know if I missed anything, have typos, or drink too much for a 2 hour job. Thanks.
Hope this helps.
Regards
GR
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