I have a 2003 Mustang GT Premium with automatic. headlights and tailights work fine. problem is the interior lights when you open any door do not work neither do the vanity mirror lights or the trunk lights. The car has the mach 1000 audio system and the head unit was dead. I removed it and put in and aftermarket unit but still no interor lights. All fuses have been checked and look fine. is there a ground somewhere i could be missing?