we have a 2004 chevy 2500 crew cab with the turn signal in the mirror. we lost power to everything in the door at the same time. the other doors all work including the turn signal in the left mirror. im assuming its a common ground but im not sure where to start looking

 

Nobody has any ideas?

 

have you checked the harness in the door jam between the body and door? sometimes wires break there otherwise you'll have to pull the switch and make sure it has powers and grounds