Odometers

Here's one I've never seen happen before.
Both odometers on my 94 Tbird have quit working. The speedometer works fine, but the mechanical dials do not turn.
Doesn't both odometers and the needle all work off the same cable?
Any ideas what to check?
Thanks for your help!
Gerri
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Yes, they do. On a conventional cable system, the cable comes into the speedometer head and a gear train drives the odometer and trip-meter sections. The speedometer part spins a bar magnet inside an aluminum cup, and the eddy currents move the needle. (With damper springs to move it back to zero, and calibrate the swing.)
If it's an electronic speedometer (which yours is probably too old to be, but you never really know till you look) there is no cable, only a pulse generator attached at the transmission where the cable would normally go. The speedometer head is a simple meter movement with an electronics module translating the electronic signal pulses-per-second to speedometer needle deflection.
The odometer and trip-meter are moved by a little stepper motor of some sort, the little computer module has to do a translation of X pulses per 1/100 mile indicated advance. With an electronic motor driven analog odometer it doesn't smoothly turn, it moves forward in a series of small jerks like the sweep second hand on a quartz analog watch.
(And for both speedo and odometer it's easy to re-calibrate the electronic systems for a different tire size, and get them within 1% accurate. On a mechanical system you have to change the transmission drive gear which is a lot more work, and if your tire size falls between drive gear sizes that might only get you within +/- 3%.)

Get the factory repair manual, and follow the troubleshooting tree. I won't even venture a guess past giving you the basic explanation of how it works. It's more likely a mechanical failure inside the speedo head, but they are too expensive to just swap out on a guess.
Speedometer heads can be diagnosed and fixed at qualified shops. They are delicate, but not impossibly so.
If it can't be fixed, you can usually order the new speedometer head with the odometer mileage set to where the old one was before it died. That way you don't have to fill out a change of indicated mileage declaration form and file it with the DMV and disclose the odometer swap to the next buyer - and if you don't follow your state's proscribed procedure for this disclosure they can accuse you of odometer tampering and make big trouble.
--<< Bruce >>--
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Something I've always wondered , ( in an electronic odometer ) where is the memory of the odometer stored ? When the battery is disconnected it still retains the original mileage .....
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Same as on my 94 'Boid a year or 2 ago. I think it's a fairly common failure. If you search the archives ...

It's not mechanical. The dash cluster is all electronic.

You can pull the cluster and speedo and inspect. The speedo is "tamper-proof". I couldn't do anything with it.
A replacement speedo with pre-set miles from a dealer was about $250 (not installed) about 1.5 years ago here in the midwest US. Check on your states odo-tampering laws.
Might consider a speedo from a junkyard. But your mileage would be wrong, unless you can figger how to fiddle the damned thang. I couldn't.

If you need more info, just ask.
Cheers, Puddin'
"Mit der Dummheit kaempfen Goetter selbst vergebens!" -Friedrich Schiller
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I have a 94 thunderchicken with the same issue, both the odo and trip odometer quit at the same time and the speedometer still works but usually sticks until you hit about 40mph or give the steering wheel a light rap then it jumps into action. I have a friend with the same year and setup and it does the same thing. I haven't looked into why it does it or how to fix yet, personally could care less about my mileage, it's depressing enough driving 32 miles one way to work anyway. But it is a common problem. And from what I have found out it is all electric, so the sending unit is doing it's job and it's with the head unit. Great driving car, comfy and handles well, if only we could keep up with the bits and pieces wearing out on them so quickly. :confused:
--
chrisnrali
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I have a 95 Tbird. Same issue. Had speedo gears replaced 2 years ago and they lasted 18 mos (c$180) and I changed out the speedo. Now I see I can buy gears and do it myself for $25-50 (depending on website for gears). The job was waranteed for 1 year
Hard part is removing the needle. I will post when I do it and put pictures/instructions on my website after post. I have read elsewhere how to remove needle.
Wish me luck.
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