Dracul

a few months ago i switched my gauge cluster to the 145mph, and now whenever the car is running with the lights off, the tach works like normal.. but if i turn the headlights on the tach doesn't work and turns backwards to around 7000rpm and then stops..

doesn't anyone know what causes this and how to fix it?

Trickster

Sounds like a problem with the ground wire.

Dracul

the ground wire for the tach or the headlights?

chevymetal

Well, since I searched, and this was the only thread that seemed to match my problems - I too would like to know. Does this sound like a ground for the tach, or headlights? I had an alarm that was installed poorly in my car, and I figured that was the cause for this problem. In my case when I turn the headlights or parking lights (anything that turns on the interior guage lighting) on, the oil guage drops to 0 psi, and the tach freezes at around 1000 rpm. I removed the alarm carefully, and completely - and I still have this issue. Any ideas?

chevymetal

Well the ground is not with the headlights, and I guess I could have thought harder and figured that out, seeing as the problem occurs with the headlights off, as soon as I turn my parking lights on. I'm going to pull the dash apart soon, and start tracing wires. Wish me luck?