I posted a problem I had with my 84' T/A's tach. Damn thing reads backwards, more like stays peged out when the engine starts. If I turn the car off and then on it goes back to 0 then when I crank it it pegs out. I tried a new tach unit w/no luck. Should only be a signal wire from the tach so I cant see where the issue is?

 

There is a tachometer filter/buffer module that may have a problem. They are often on the instrument cluster. Corvettes have them near the distributor. I'm not certain where it might be on an '84.

 

Yea, thats what I was thinking too but the schmatics in my manual do not show this buffer. I took the cluster apart and couldnt find it. It dawned on me the other day that it might be inside the HEI witht he coil. I'll check it out.

Thanks for your help.

 

It's a circuit board on the back of the tach itself. Looks a bit like this.

You need another one.

BTW, the part that's circled, is the factory-trimmed thick-film resistor {insert Flintstones theme here} that changes value, and makes these read high all the time.