84 speedometer no power (Page 1/1)
JarHead389 SEP 19, 12:41 AM
hey all - i've just picked up my first fiero the other day, slowly working through some of the issues to get it driving.

one of the bigger ones that i'm having no luck figuring out is the speedometer, which seems to have no power at all. needle doesn't reset to zero, odometer doesn't work, trip odo doesn't work either. no idea if cruise works.

there is no check engine light so i believe the VSS is functioning properly, it's just the gauge itself that's completely dead. any advice on a repair or replacement? (preferably repair so i don't have to find an 84 speedo w/ cruise)
82-T/A [At Work] SEP 19, 08:03 AM
What kind of condition are the gauges in? Do you see rust everywhere? Is the car otherwise in good shape?

First thing I would check is the plastic sheeting behind it that has the leads on it. This was very common for gauge clusters back then. Sometimes the leads break where they connect to the connector, and then there's no connection.

My daughter is restoring her 85 Fiero, and she sent off her gauges to Jack Gunsett who tested the entire gauge cluster, all the components, tuned them, and repaired them. He did an awesome job.

He made a video for my daughter, which she introduces here, so you can see everything he does:
JarHead389 SEP 19, 09:16 AM
the rest of the gauges are in good shape and seem to work, though their accuracy is still up in the air (temp gauge...). the rest of the car is in decent shape as well

this morning i hooked just the speedometer up since i've got the rest of the cluster pulled and probed around with the multimeter. i measured +10v coming in (the battery is probably a bit low) and power going to the chips on the board but still no life from the gauge. any ideas?

[This message has been edited by JarHead389 (edited 09-19-2025).]

82-T/A [At Work] SEP 19, 10:02 AM

quote
Originally posted by JarHead389:

the rest of the gauges are in good shape and seem to work, though their accuracy is still up in the air (temp gauge...). the rest of the car is in decent shape as well

this morning i hooked just the speedometer up since i've got the rest of the cluster pulled and probed around with the multimeter. i measured +10v coming in (the battery is probably a bit low) and power going to the chips on the board but still no life from the gauge. any ideas?





If you can verify the VSS is working, it could be one of the servo motors. As you can see... the speedometer and odometer are driven by motors, rather than cable driven like the older cars. I can't remember if he mentioned it in the video, but the servo motor was bad on my daughter's gauge cluster, and he replaced it. For me, I think it was just the odometer.
JarHead389 SEP 19, 10:13 AM

quote
Originally posted by 82-T/A [At Work]:
If you can verify the VSS is working, it could be one of the servo motors. As you can see... the speedometer and odometer are driven by motors, rather than cable driven like the older cars. I can't remember if he mentioned it in the video, but the servo motor was bad on my daughter's gauge cluster, and he replaced it. For me, I think it was just the odometer.



my understanding is that a bad VSS will throw a check engine light, which i don't have so presumably the VSS is working. the motors being the issue doesn't make sense to me because neither the speedometer nor the odometers show any signs of life. the speedo needle doesn't even reset to zero by itself.

my best guess is an issue on the board itself but other than checking voltages i'm a bit clueless on how i would diagnose the issue.
1985 Fiero GT SEP 19, 11:36 AM

quote
Originally posted by JarHead389:


my understanding is that a bad VSS will throw a check engine light, which i don't have so presumably the VSS is working. the motors being the issue doesn't make sense to me because neither the speedometer nor the odometers show any signs of life. the speedo needle doesn't even reset to zero by itself.

my best guess is an issue on the board itself but other than checking voltages i'm a bit clueless on how i would diagnose the issue.



84 and 5 speedos don't reset to zero, along with the other gauges, it stays where it was reading last/where it is bumped. The ECM gets the VSS reading from the Speedo board, the Speedo board gets it from the transmission and converts it to something the ECM can read, so either it hasn't quite hit the parameters to trigger a check engine light, or at least a significant part of the Speedo board is working (or your check engine light bulb is burnt out? Just a thought).
JarHead389 SEP 19, 12:08 PM

quote
Originally posted by 1985 Fiero GT:


84 and 5 speedos don't reset to zero, along with the other gauges, it stays where it was reading last/where it is bumped. The ECM gets the VSS reading from the Speedo board, the Speedo board gets it from the transmission and converts it to something the ECM can read, so either it hasn't quite hit the parameters to trigger a check engine light, or at least a significant part of the Speedo board is working (or your check engine light bulb is burnt out? Just a thought).



that is very interesting, the check engine bulb isn't burnt out so it definitely doesn't have a code set. i'll have to do some experimenting and see if i can get proof of life for either the VSS or the speedo.
fierofool SEP 19, 03:38 PM
If you can or have removed the VSS and the gear is still there, remove the gear and chuck the VSS into a power drill. Power the drill and see if the speedometer moves. Switch ON, of course. That should tell you if the VSS is good or bad.

Even if the gauges are bad, as long as the ECM is seeing a VSS signal, the car should run OK. If there is no VSS signal, it will run like crap because the speed tables aren't matching with the Throttle Position Sensor tables and other look-up tables.