Speedometer not working - '85 GT (Page 1/2)
bincitybandit OCT 15, 06:39 PM
First post here, just bought a Fiero yesterday!

It is an '85 GT with manual transmission and V6. Speedo, odometer, and tripometer arent working. The speedo is stuck on 17 mph, never moves. All other gauges in the cluster are working. Radio works, fuse is good. I pulled the VSS to check the gear, which looks fine. Stuck an ohm-meter on it while I had it out, and got signal while turning the shaft and the VSS, so I am assuming the speed sensor itself is good. The "check engine" light is NOT on, and I don't have any way to tell if it is throwing in codes.

So I assume I am now looking at an electrical issue in the cluster itself.

Hoping someone may have some guidance on what to look for next.

[This message has been edited by bincitybandit (edited 10-15-2019).]

olejoedad OCT 15, 06:56 PM
The speedo circuit plugs in to the bottom left side of the instrument cluster surround.
Take the lower trim piece off and its easily accessible.
Patrick OCT 15, 06:59 PM

quote
Originally posted by bincitybandit:

I don't have any way to tell if it is throwing in codes.



Got one of these?




Have a look Here.
bincitybandit OCT 15, 07:28 PM

quote
Originally posted by olejoedad:

The speedo circuit plugs in to the bottom left side of the instrument cluster surround.
Take the lower trim piece off and its easily accessible.



OK thanks, I have it all apart so is accessible. Now that I can access it, what am I looking for??

bincitybandit OCT 15, 07:41 PM
I have 12 volts on two of the pins in the connector that plugs in directly below the speedo..........
olejoedad OCT 15, 08:19 PM
Find the yellow wire and the purple wire.
Hook the DVM across the two.
Put the DVM on frequency, spin the speedo gear and look for the result.
That verifies the integrity of the wiring to the dash cluster.
bincitybandit OCT 16, 05:38 AM
Thanks, the ohm-meter indicates continuity between the yellow and purple wires while driving the car around the yard. Seems to confirm further that the VSS is working and signal is getting to the dash cluster.

I have the cluster completely removed. When I manipulate the needle, it seems to always find its way back to the 15-20 mph area. I read somewhere online that this may indicate a bad coil on the speedo itself? If that is the case, is there a fix to that problem, or would it need to be replaced?

Having said that, I've noticed while looking online at various places for used speedometers, that many of the ones available pictured at various vendors, seem to also have the needle pointed in that 15-20 mph area. Perhaps I am not on the right track.

I should probably also add that the cruise control does NOT work.

Lastly, after learning how to access the diagnostic codes (thanks Patrick!), it is throwing code 24 which relates to the VSS. However, based on the code tech sheet at the Fiero Store, it says to disregard this code when the vehicle is not in motion.

[This message has been edited by bincitybandit (edited 10-16-2019).]

olejoedad OCT 16, 10:18 AM
The next place to check is for corrosion on the plug and the speedo board.

I have speedos if you need to replace it.
bincitybandit OCT 16, 10:27 AM

quote
Originally posted by olejoedad:

The next place to check is for corrosion on the plug and the speedo board.

I have speedos if you need to replace it.



No corrosion, everything is nice and shiny, and looks fine.
olejoedad OCT 16, 01:57 PM
Forum member JGunsett also calibrares and sometimes can repair.