How can I bench test A 1987 Trans Am electronic Gauge cluster My speedometer is not working And I'm not sure if the sending unit is working either Everything from the cluster works except for the speedometer They no longer fabricate and I cannot find the sending unit for a T5 So before I purchase A GPS sending unit I just want to test the speedometer to see if it actually working

 

You can fill out your car details and possibly a location here.

Check the vss connector for voltage with key on.
Then if wire A has +5v, plug it back in and check wire B with a tachometer while the car is on stands, running some speed.
If bad, mech speedo gears and a thread-on VSS like Jags That Run sells will work. You'll need the 4004 pulse/mile version.
https://www.thirdgen.org/forums/tran...-vss-help.html