hey, I just finished putting a 350 Carbed into my 87 Formula it was orignally a 305 with a T-5 but when I got the car the 305 was long gone, so I put a motor in it and the speedometer and the instrument cluster lights do not work, the dummy lights and all the other gauges do.

Anybody have ideas? Ive been reading about the VSS going throught the ECM does my cars speedo go through the ECM?

 

Yea I said something stupid.. Ha. happens. I reread it. I would say it is probably a ground was knocked off somewhere. Since the speedo or the ECM would have no bearing on the cluster lights, and with the speedo being electronic, maybe they share a ground.,

 

one question... what would a TPS sensor have anything to do with a speedometer?

 

not a bloody thing....


The speedometer on that should have been electronic. Trace the wires from the VSS at the tranny and check for any breaks in the wire along the way.

I cannot remember for sure if the speedo goes through the ECM or not, something tells me it did...

 

Well I dont think I ever hooked up the body ground would that effect it?

 

possibly? I am not sure, I do know that unless you hook up every ground odd things can happen.

 

Well I just put in a new 140 Speedo and its stil doing the same thing all the dummy lights work and all gauges except speedometer and the cluster lights.

I'll try the ground tommorow its getting dark out.

 

Yes, give the ground a shot...

Bad grounds cause some pretty wacky stuff!

 

Well I hooked the ground up and nothing, but I found my problem I tracked the VSS wires the purple and yellow one into my car and found that they are not connected any body know wheres these connect at inside your car?

 

http://www.hioutput.com/tech/speedo.html
this should help you out