88GT:

So my odometer stopped turning but my trip odometer, tach, and speedometer work fine.

Does this eliminate any wiring or connector issues outside the instrument pod? Does this mean it's an odometer motor that went bad? Or what else could cause this?

And is there any way to test the odometer with the cluster out of the car? e.g. Can I hook up voltage to a couple posts and get the odometer to turn without it installed in the car or do I need a functional VSS signal?

Can be several things...
motor or speedo board bad.
dirt in odo
broken odo counter

see https://www.fiero.nl/forum/.../HTML/145251.html#p1

------------------
Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should.
(Jurassic Park)

The Ogre's Fiero Cave

quote Originally posted by theogre: Can be several things... motor or speedo board bad. dirt in odo broken odo counter see https://www.fiero.nl/forum/.../HTML/145251.html#p1

From the other thread:

2 drive 2 stepper motors for odo and trip

Your problems is #2.
The board or oddo motor might be bad.
The counter might be bad.

"Easy" way to look...
You have to pull the gauge front trim and "glass" and have a camera to watch the odo when you drive"

What am I looking for with the camera to give me an indication whether its the board, motor or counter?

The gear will move when driven.

Can bench it but faster just "watch" while driving.

Front trim is easy to remove. Gauges have own screws hold them in.
plus can often see if just "dirt" trapped in the gear at right side of counter.

Better to remove front and bottom trim to remove the speedo anyway. Save messing w/ entire dash and steering column and breaking other parts.

If trip odo works then Not a board problem.
Just look at a spare and both motors are wire in parallel to same 2 driver chip pins.

But think motors may spins opposite because plug is wired + - - + (or - ++ - ) If the motors care about polarity.
motors are covered in US patent 3495113A 3469132A and don't have time to read.

[This message has been edited by theogre (edited 07-16-2021).]

The trip, odometer and speedo all work from the same signal. If 2 are working the servo motor has stopped working for the trip odometer. You have a PM.

Jack

I had that problem and was advised to wiggle and push the odometer reset button while driving. It fixed the problem. Try it, sometime the problem is an easy fix.
HarryT

quote Originally posted by HarryT: I had that problem and was advised to wiggle and push the odometer reset button while driving. It fixed the problem. Try it, sometime the problem is an easy fix.

That should only affect the trip odo.
When you push the Reset Button on the Trip Odo, you must push and release slowly and if needed push 2 or more times to see all 0's inline.
Trip Odo can get stuck, even damage it, if resetting fails.
GM has several TSB just saying same for Fiero and some other models.

Dirty Main Odo gears can cause same problems.
Motor tries to turn but jam gear(s) won't move or can break.

Odo Counters are easy to break because has small plastic parts.
Trip have some more parts you see easy because of reset function but main odo works the same plus has "anti-tamper" parts to prevent people "rolling back" the odo for sale of car.