Rear defroster problem
 

Hey all:
My rear window defroster seems to work once in a while. Just wondering what the cause of that could be even though the switch will turn off after a while as it should. I am going to sand the connections on the combination relay just to see if that cures the problem, but because it turns off after 10 minutes, which is controlled by the relay, can the relay still be bad or does it have to be a wiring issue? Thanks.

Anyone? I can't see out of my rear window as it is raining in Philly. Someone please help me out here.