Stereo works until lights turn on then it shuts off?
Hello I just installed a new stereo in a 1977 comaro. The comaro had 3 wires that looked like ground so I hooked my stereo up leaving the 2 extra wires. When I turn the car on the stereo works fine and plays loud. Once I turn the lights on the volt meter goes crazy. The stereo cuts out. The lights flicker then shut off. And then the stereo comes back on once the lights are off? I'm thinking it's a grounding issue and I should wire a direct wire from the stereo to the battery ground? Any advice?