It does what if you go up a hill?
A simple trick to finding a short is to replace the blown fuse with a pair of spade terminals, then use small jumper wires to connect them to a 12 volt light bulb. A brake light bulb works well. When the circuit is live and the short is present, the bulb will be full brightness and hot so be sure it's not laying on the carpet or against a plastic door panel. Now you can unplug electrical connectors and move things around to see what makes the short go away. When it does, the bulb will get dim or go out.
In this case, since it's a relatively high-current circuit, you may need to use a head light bulb. A brake light will only allow about one amp of current to flow through the circuit. A 9004 or similar head lamp bulb will let at least five amps flow. That will be enough to make the fan motor run, even though it will be at a reduced speed.
That circuit breaker is in the wrong part of the circuit to be of any help in diagnosing the cause of the problem because it is protecting too much stuff. That COULD be a clue, however. There could be broken and frayed wires between the front door hinges that are touching intermittently. If there are, you'll see the test bulb flicker in brightness when you open and close the door.
Do you have automatic temperature control?
Thursday, December 12th, 2013 AT 1:48 PM