A 2005 Ford Expedition with a 5.4 liter engine was blowing the fuse for the air conditioning compressor every time the PCM commanded the compressor ON. I started checking for shorts in the wiring by disconnecting various parts and checking resistance, but found nothing out of the ordinary.
I reconnected everything except the field coil and the fuse stayed intact. Connected the field coil again and the fuse blew. It was obvious at this point it was the field coil causing the fuse to pop, but I wasn't sure why since the resistance reading was normal. I decided to pull the clutch plate and pulley off to find the cause of the problem. I found the epoxy in the field coil winding had deteriorated so badly that the winding wire had come loose and was apparently rubbing the back side of the pulley when it energized, causing the fuse to blow almost immediately.
