Does anyone have knowledge of testing a speedometer 4 output buffer?
I have enough electrical knowledge to be dangerous.

I have a V6- '86 firebird and the speedometer (electronic not cable driven)has stopped working, I have a pulse signal to the buffer from the tranny but no signal out of the buffer to the speedometer. It does have a signal out of the buffer to the ECM and cruise control. If i disconnect the cruise wire and hook the speedo wire to that connection I no longer get a signal out. I believe the buffer is bad then. Can anyone to verify my theory.
Anyone ever test one like this? Could the speedometer be bad and not allowing a signal from the buffer no matter which output its on?
Thanks for the help.

 

That sounds more plausible. One of the simplest explanations could be that the speedometer wire is shorted somewhere along its path and thus shorting out the output from the buffer box, no matter which output you use.

I'd recommend disconnecting the speedometer connector behind the cluster and checking the output from the buffer box. If it works now, it's not the wire, it's probably the speedometer itself.

Hope this helps.
Lou

 

Thanks for the advice. I'll give it a try.