Gauge reads hot with lights on

[VegasFastback]

When I step on the brakes the temp gauge tick up. When i turn on the headlights it does it worse. Doing both is enough to peg it. I'm assuming bad ground, but I don't know where to look.

 

[Don C]

I agree with the bad ground. It could be either (or both) the chassis ground or engine ground. I would start with the chassis ground, which is usually on the bottom screw of the voltage regulator, and then goes on to a bolt on the engine block.

 

[will e]

Also agree with bad ground. Simple test is to hook a wire up from negative on the battery to a good body ground (shock tower bolts work).