Hi all I知 working on installing a backup camera in my 2002 ML320 which had the FO Bose. Current head unit is an1300nex pioneer. I know my reverse lead is in the C harness (gray wire C3), but when I test with voltmeter, the voltage is 7.3 when I知 parked and 14 volt when I知 in reverse. I connected my head unit reverse wire but for some reason it doesn稚 automatically switch when I shift, and I think it痴 because the voltage never drops to 0 when in park. Any idea why this is?