Lights Dim Slightly

1997 Grand Am SE
3.1L V6

I recently noticed all my lights seem to get slightly dim for a brief moment than back to normal. This is constant as long as the car is running. When the car is not running and the lights are on, they are normal. My mechanic suggested I run a new ground wire from the body of the car to the engine. I mentioned my A/C compressor just seemed to short out for no reason and suggested the possibility the two problems may be related. Does anyone have any ideas on why the lights would dim while the engine is running???

Thanks again all

1997 Grand Am SE
3.1L V6

I recently noticed all my lights seem to get slightly dim for a brief moment than back to normal. This is constant as long as the car is running. When the car is not running and the lights are on, they are normal. My mechanic suggested I run a new ground wire from the body of the car to the engine. I mentioned my A/C compressor just seemed to short out for no reason and suggested the possibility the two problems may be related. Does anyone have any ideas on why the lights would dim while the engine is running???

Thanks again all
Could also be a bad alternator maybe? The only time my lights dim are when my subwoofer hits and I have my foot on the brakes :p