poor-sh-nut

My odometer doesn't work but the speedometer does. I checked the odometer gears and they look fine. Could the Speedometer Impulse sender on the transaxle cause the odometer not to work?

thirdgenbird

i think if the speedometer works but not the odometer its got to be gear related. ive been told you cant always tell by looking and it. it also could have slid away from the worm gear

KuHL 951

Did the odometer work when you bought the car? If not, then someone probably pushed the trip reset button while the car was moving. It will strip the odometer gear very easily.

Here's the fix:

Odometer Repair

Eric_Oz_S2

The only cause of odometer failure if the speedo is working is mechanical failure in the speedo/odo unit. You will need to check all of the gears. You can spin the gears with the speedo disassembled and work out where the problem is.

CurtP

It can't. When the solenoid is engaged, it pulls the shaft with the digit driving gears away from the digit cluster. There's no strain on the gears with the reset button engaged. Every one that I have seen fail has been because the one gear has deteriorated and falls apart.

onefastviking

+1
I think thats just when many people notice it because they then are focused to the odometer, probably like that for miles before.

onefastviking

FYI - Many times the gear has pushed(moved) slightly on the shaft not allowing it to engage the other gear. It looks good at first glance but look close and you will see.

KuHL 951

My bad. I assumed Clarks Garage was correct and this is the first I've heard it's OK to reset the odo while moving. I learn something new every day. Is Clarks gear replacement procedure correct?

CurtP

It gets repeated here quite often and is generally accepted as correct. The only correlation I can see is that if the gear is deteriorated, and you reset while in motion, the slipping of the cogs on the gear is enough to shear a few teeth. Have you seen what the gear looks like when it's about to let go? It gets soft and very rubbery and literally disintegrates on contact. I've never seen anything like it and it only affects that one gear (of course, it's the one that's a PITA to get to).

Porsche changed the design of the speedometer in (I think) '89 and it doesn't look anything like it did. It doesn't have the problem with the odo gear. I'm running the newer assembly in my '87 housing without issue.

The writeup at Clarks is ok, but it is severely lacking in detail (and pictures). At one point I started to document it, but I never finished. The hardest part of the whole thing is removing the needle without damaging it, the shaft and/or the movement. Personally, I think it should be done professionally so it won't get damaged and can be re-calibrated after the repair.

Sysgen

My car is a '90 and I had to replace the gear also. So I don't think they changed that gear in '89. It also has happenned right after I pressed the reset button. Teeths were missing on the gear.

CurtP

I happen to have my dash apart right now (prepping for windshield #4). I was planning on taking the bezel off the cluster to inspect the light tunnels. If I get to it, I'll take a picture of the speedometer I'm using so you can see the difference and I'll look for a date code.