hey

Are you tryng to install an aftermarket tach, or repair the factory tach? If you are hooking up an aftermarket tach, you will have to find the wire that sends the firing signal to the ignition coil (or coil pack). On cars with a factory tachometer, the tach function is driven by a microprocessor in the instrument cluster. This processor receives an RPM signal from the pcm and translates that into tachometer needle movement. Any decent aftermarket tachometer will have an instruction sheet that tells you what kind of signals the tach is compatable with and gives you an idea where to hook the signal wire.

if your buying a aftermarket one it tells you what to wire it too... and you will find yourself wire one of the coil packs

Ok I have a 2001 cavalier ls and I put an after market in it and I hotwired it and now my gauges are not working and that's the only thing not working what might be problem