odometer failure

[nickgardner]

at 61,000 miles my odometer has stopped working. speedo is still going fine

a quick look onllne shows various articles and youtube videos on cause (failure of small plastic gear inside the unit) and how to repair.
Almost all (possibly all) seem to relate to a unit with separate mechanical trip counter. my car has the electronic computer (or whatever you call it) which features an electronic trip, which I assume is why me speedo has no separate trip. anyone know if this affects the usefulness of the articles etc relating to models with separate trip?
anyway any tips/advice on how to get it repaired? I can see getting the unit out of the dash is not that difficult but my preference would be to then send it to someone skilled and experienced for the actual repair. I don't want to replace the whole unit if it can be avoided as trying to preserve authenticity and the actual mileage.

thanks

 

[matthewb]

Hi Nick

I had exactly the same problem - I own a 993 C4S too.

These links should help you.

• https://www.porscheclubgb.com/forum/tm.aspx?m=836294&high=odometer
• http://p-car.com/diy/odometer/
• http://www.odometergears.com/products/Porsche/911-993+94-98+%28Non-US%29/73

I have a Word file I created for Maurice et al - let me know if you'd like more help and I can email it to you..

 

[pse_SC]

If you’re based anywhere near North London (South Harrow to be precise), then Julian Reap is your man.
Pop the speedo out carefully from behind the dash and get it over to him. What he doesn’t know about them isn’t worth knowing []
If the main odometer (mechanical) not working, then it’ll be a cog or two - he often has a supply and can fix.
It’s not as easy as it looks(!) - taking care of the needle and replacing it accurately is the big thing... watched him do this for mine.
See:
http://www.reapautomotivedesign.com/index.php

 

[T911UK]

Julian did mine last year,

 

[nickgardner]

thanks. v helpful

 

[nickgardner]

thanks a lot. not sure Im brave enough to have a go myself given the delicacy but this confirms where I had got to on it

 

[matthewb]

Thanks for giving me 'Best Answer'.

I wrote this a while ago ...


===================

This odometer fix is intended for those 911/993s with an OBC display in the tachometer dial – i.e. there is no mechanical trip-meter in the speedometer dial. It is largely derived from the article on the www.odometergears.com website which covers those speedometers with a mechanical trip-meter in the dial. My car is a 1997 Carrera 4S with a 993.641.538.00 speedo.

PROBLEM: Your speedometer works, your odometer does not. The chances are that the tiny, little 15-tooth plastic planetary-gear that drives the odometer from the speedo sensor has turned into soft gel-like rubber over the years, apparently due to excessive heat and a corrosive oil lubricant.

Note that this fix is not difficult but it is risky. The most finicky point of this fix is dealing with the removal and reinstallation of the needle pointer onto its shaft. The shaft of the needle is tiny... very tiny. Damage this and you are looking at replacing your speedo.

STEP 1: Speedometer/Odometer Removal
To protect the dashboard, slide an old credit card under the rubber retainer-ring behind the speedo trim-ring and then, using a wide, cloth covered screwdriver, gently prise-out the speedo - once you've got it started, just hold it firmly, twist gently and pull slowly. The rubber retainer-ring comes out along with the speedo. Finally, unplug the connector.

STEP 2: Trim-ring Removal
Remove the rubber retainer ring. Remove the 4 screws from the back of the unit. Now the soft aluminium trim-ring with glass needs to be 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. Go slowly and 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 the trim-ring can be pulled off. Then drop the workings out of the case being careful with the needle.

STEP 3: Speedometer Needle Removal
Before beginning, make a note of the Speedo's zero position. Carefully rotate the needle anti-clockwise whilst gently prising/lifting the needle - do not pull straight up. The needle is pressed onto an extremely thin shaft - friction is all that is holding the needle to the shaft. Keep turning and applying a small amount of upwards tension until the needle comes off. Do not force it. Note how thin the shaft is - be very careful with it.

STEP 4: Disassembly
Remove the two small black screws from the faceplate. The whole unit should now come apart. Remove the four screws holding the PCB in place. Remove the 2 screws holding the motor in place. Once the motor has been removed, you will get to the drive-gear and pod. Inside the pod there is going to be a small, yellow, probably broken, planet-gear. Note which way around the planet gear fits. Check that the large green pod drive-gear is OK.

STEP5: Acquire Replacement Cog-Wheel
Order appropriate new small planet-gear and/or large pod drive-gear as required from Ododmeter Gears - www.odometergears.com and wait for the package to arrive. I only needed to order a 15-tooth planet-gear.

STEP 6: Cleaning
Blow-out the whole assembly with compressed air. Don't forget the motor itself - at the base of the metal spindle are very fine teeth that must be free of any debris. Then, using meths or white spirit and cotton-buds, clean the oil/gunk off gears, pod, stepper-motor rotor and spindle. Ensure everything is spotless using a strong light and magnifying glass. Do not apply fresh lubricant - there is no need.

STEP 7: Reassembly
Rotate the drive-gear and check that it spins freely - if it is not free-spinning the stepper-motor will not be able to turn the odometer. Place the new 15-tooth planet-gear on the shaft of the pod and verify that it spins easily - the stepped part of the planet-gear faces up towards the motor. Place the pod and gears inside the main assembly and spin it with your fingers to verify that everything is seated correctly. Now, install the motor assembly through the pod. While doing this, use one finger to gently rock the one's digit back and forth. Continue doing this while tightening the screws for the motor assembly. Using the exposed black main-gear, manually wind the odometer forward a few miles to make sure there are no sticking points. I put on several miles just checking everything felt smooth - it should feel smoothly, consistently, ‘notchy’ due to magnetic resistance from the stepper-motor. Then reassemble the speedo in the reverse order of disassembly, although I suggest not refitting the trim-ring and glass until you've driven a few miles and checked everything is working. If the odometer doesn't tick-over, remove the speedo and go back to STEP 6.

 

[nickgardner]

for anyone interested I followed the advice and got Julian Reap to do it. top job and well worth 130 odd quid to preserve originality and not mess it up myself. getting the speedo out and in is straightforward - its just an interference fit with the rubber surround sleeve into the dash. i levered it out carefully using some plastic bodywork/trim tools - £10 or so on amazon for a set, going slowly and carefully. put it back in with a smear of fairy liquid round it to aid manoeuvring. connections to it re electrical and easy to remove.

 

[Graham-S]

I have an issue with my Oil Temp that keep going hi and if you tap it is drops back to normal
I took it apart (behind Only) and resoldered all the connections hoping that would sort it but alas it still does it.
I'm guessing its the little motor/pot that has the fault. Would Julian be able to fix that??

Graham

 

[nickgardner]

not sure but drop him an email via his web site. he takes a few days to reply

 

[Graham-S]

Hi Nick
Did email via his website last week not heard back yet
Graham

 

[anthonyhunt]

Have had my odometer repaired by Julian Reap-first class job anyone who has this problem send your unit to him.