hey all,
1985 gt v6 auto trans, speedometer not working.
trip odometer is working. get out on highway and speedometer
needle moved to around 80 mph.
mileage odometer not increasing in distance.
did not notice if mileage odometer changed during the highway trip.
might check if it dose later.
I looked at all the past posts of speedometer topics and
I am overwhelmed by the possible causes.
suggestions greatly appreciated
have a great day

I would be looking for a different speedo.

The trip odometer is working, so you have a VSS signal.
The regular odometer may or may not be, it could be a bad stepper motor, stripped gearset or lack of signal from the speedo board.
The speedo doesnt read correctly, again, it could be a bad speedo board.

Can you read speed from ECU with scan tool?

I don't have a scan reader. the pin is between 10 and 20 mph position at rest.
thanks for the input.
Parts are scarce her in Va.

I recently went through troubleshooting a non-functioning speedometer on my Fiero. My speedometer didn't move at all while moving.

Do you have any check engine lights? Can read codes by jumping the ALDL connector behind the cigarette lighter panel.
//www.fiero.nl/cgi-bin/main.cgi?ECMCodes

Like olejoedad mentioned, it kind of sounds like something in the speedometer assembly. You can pull the plastic panel from under the dash/steering column and there is a plug that goes straight up on the left side. You can verify it didn't come loose and re-seat it to ensure it has good connection.

I'm not familiar with the auto trans (mine is manual), if you can carefully pull the VSS off the transmission you can verify the gear didn't break or fall off and you can test the VSS by using a multi-meter set to AC and spin the VSS shaft with your fingers. There should be a small amount of voltage that is generated. If it reads zero all the time while spinning, the VSS is bad. You can youtube search how to test a VSS or vehicle speed sensor to see videos.

If you decide you think it's the speedometer, it should be easy to pick one up from someone in The Mall to replace it. New VSS's are available from autoparts stores for automatics.

thanks,
the only lights I have in the dash are the ajar light.
turn signal bulbs don't light up when actuated.
the ses lamp is not on either.
checked a few bulbs and they appear ok.
panel is dark on speedo side and tac side is lit up.
so I will try the jump to the plug and see what happens as far as the
ses is concerned.
is this mainly the engine check of sensors?
what info would be to my advantage for the speedo. thanks for your time.

By the sounds of the lights not working on parts of the dash it would seem there are bad connections. Possibly the printed circuit board in the dash is separating and gone bad. The check of the SES lamp was to see if you had the code 24 for the VSS. I doubt that's your problem. I'd focus in on the dash, check the printed circuit board and see if there are any bad spots. Maybe start looking for a good used cluster to swap in.

bulb was missing on check engine light,replaced
got these codes
21,23,35.
on code 35 what does iac stand for.
thanks again