Trying to install a used aftermarket head unit on my Colorado. I noticed that the head unit has a ground wire that was previously ground to the chassis. The adapter harness (left below) also has a wire that says chassis ground. I see that I have two options. What do you recommend?
1. Ground aftermarket head unit directly to chassis with a self tapper and leave the adapter harness ground unattached.
2. Connect both the head unit ground and the adaptor ground together hoping that the radio grounds through the harness?
I've done the first one. If you have an amp I think it can cause the alternator whine? Mine does it occasionally. Someone smarter than me will chime in.
Use the chassis ground. Learned that the hard way. Installed an aftermarket radio in a Renault Alliance years ago. Matching wire colors didn't work so pulled out the multimeter and figured out what wire was what on the car and found a ground wire in the harness. So I used it. It kept popping fuses in the car so I changed it to chassis ground and worked as advertised.
