K, when I started my car (just bought it 84 z28 HO), the tach pegged high when started, so I bought a new cluster off ebay (guy claims it worked great when removed from an 85 z28), problem is, now tach works, but is WAY off, Idles at 2500rpm, pegs at probably around 2500 true RPM. Is this what would happen if it's a v6 tach(what I suspect)? Tried intermixing parts with the old tach, but the problem is on the circuit board, so that won't help, swapped the little yellow box on the back of the cluster, didn't help.....

Anyone know what the voltage should read to ground on the tach wire (ie conversion volts to rpm)?

Any help would be appreciated.

Thanks all

 

Sorry forgot to ask, would it matter if the new tach came from a tpi car?? Not sure if it did, but would it matter?