why do my guages go crazy when I turn the reostat on my headlight switch?

Asked by Sep 01, 2014 at 10:20 AM about the 1965 Pontiac GTO

Question type: Maintenance & Repair

When I adjust the resorts on my headlight switch my temp, oil, and gas gauges pin until
I completely turn resorts all the way counter clockwise. ANY IDEAS?

3 Answers

35,615

Did it get wet? Or..........You haven't been messing around with anything electrical lately have you?

Best Answer Mark helpful
70,945

When you say "pinned" do you mean the gauges go to Full, Hot, etc.? Or the other way? When I first bought my '70 Catalina the gauges would all go to Empty, Cold, etc. when I switched on the headlights. The turn signal indicators and high beam indicator would light dimly as well. The problem was a bad ground at the instrument cluster. The previous owner had installed an aftermarket radio and forgot to hook one of the ground straps back up to the instrument cluster. HTH. -Jim

Best Answer Mark helpful
4,805

The rheostat is probably bridged with metal worn off over time. Then that happens, there is a surge of current draw at different areas of the rheostat. You can get an authentic aftermarket replacement switch for that car from Ames Performance, OPG, or Performance Years. I would agree with JS08016 also - check the ground to the instrument cluster as well as the ground connection at the headlight switch. Any stray voltage coming off the rheostat seems to be finding it's way to ground via the gauges.

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