My installer didn’t mess with factory head unit either. I left it factory and just did amps and speakers.
And correct power is coming from battery. I have had an awe full time with this dealership. Just ironic that same day I pick my car up from getting new speakers that I get wrench light. I turned off in parking lot and turned my car off. It wouldnt start back up. After about 45 minutes for what ever reason it did start back up. I then got it to the dealership where at first they said was clutch pin (I think) they tried blame that on audio also. My gut feeling is that I have had many issues and with this dealership that They are trying to not fix it under warranty.
this stuff is all new to me. So thank you for responding.