If you unplugged the radio and the blower motor, you have to have a dead short for this to happen. In your owner's manual, check to see what circuits that fuse covers. Also, I would recommend checking the wiring from the heater switch, to the relay, resister, and then motor for shorts. Do the same with the stereo power supply. There has to be a bare wire at some point that is grounding.
Let me know what you find.
Monday, December 21st, 2009 AT 8:24 AM