I currently have an 88 IROC 305TPI A4. the guages work perfectly when the headlights are not on. When I turn the headlights on after a few minutes(3-5) the tach goes nuts and either pegs at 7k or bounces all over the place. The right turn signal indicator light also lights up and the lights for the tach guage goes out. My initial thoughts were this was a bad reostat in the headlight switch. I have replaced the switch with a new AC Delco switch and I am still encountering this problem. Another symptom is the battery gauge will actually tick up and down 2 volts when the turn signal is engaged and the lights are on. all the exterior lights work fine and I am leaning towards a bad board for the guage cluster does that sound correct before I start trying to track down another one?

I have looked for any obvious signs of broken wires or bad grounds but cant seem to find anything thats why I am turning to the experts. Am I on the right track or overlooking something

 

Well I have been working on this issue and feel like I have narrowed it down to a bad ground. After narrowing it down all the exterior light sockets were removed and checked and no bad grounds have been located.

I guess my question at this point is: Is there a non intrusive/good way to splice into each ground wire going to the socket and have a long wire grounded on the body until I can figure out exactly which wire is causing the problem. I am not an electrical genius but there has to be an easier way than stripping the covering and splicing into each wire and then taping it up afterwards.

Help, Please.

 

 

Did you ever find the problem, cause I'm having the same identical problem, let me know if you did?