Working on my friends 84 Recaro Trans Am and the tach doesn’t work. Could anyone supply a diagram or pictures of how it functions? Chiltons and google was no help. Car has alot of vacuum leaks currently working through them. He said tach used to flutter and now it just sits dead.

 

My guess if it fluttered before it was starting to die noe it is dead.

It properly needs to get rebuilt.

 

Not too much in the way of "how it functions". It takes 3 things to make it work: 12V, ground, and the signal from the ign coil.

As Top says, if it "fluttered" for awhile and then died, it's most likely ... dead. Only problem is, there's no "rebuild" that I know of. (speaking as someone working on that exact problem just this afternoon)

 

Okay TY fellas. Just to verify, which color wire should I be checking on the Ignition Coil? and if the factory tach is shot, does anyone know which pin or color wire on the interior gauge connector is the wire that sends power to tach and the one that goes to coil?

 

The wire the tach looks at for its signal is the white wire at the coil. AFAIK it's white all the way through to the cluster connector.

The tach gets its 12V from the same connector pin and PCB traces on the "circuit board" on the back of the cluster as all the rest of the gauges. If all of them work, there's probably no issue with any of that.

 

Thanks Sofaking you have been very helpful, I will check the wire

 

You can hook up your oscilloscope to it and see if there's ignition pulses (12V most of the time, goes to ground on a regular basis for a few milliseconds at a time to fire the coil); and if it looks like that, it's pretty much gotta be the tach itself.