There was a service bulletin that applied to older models. When the door is open, rain water runs down the edge of the roof and drips into the power mirror switch. Once a little corrosion occurs, a little current flows. The current leaves a trail of carbon behind which conducts more current, and pretty soon you have a melted switch. Just replace it before you go looking for a complicated cause that may not exist.
Replacement switches were supposed to be sealed to prevent this from happening again.
Friday, March 20th, 2009 AT 8:12 PM