Appears I found the problem, it was in the blower selector switch. When the selector switch is turned. Inside the switch it creates continuity to both a set of positive terminals and a seperate set of ground/negative terminals. The switch became defective (over 300,000 miles) and apparently, inside the switch it is bringing continuity from the positive connections to the negative and then of course grounding and blowing the 10a fuse. The repair of course is to replace the blower selector switch. Also, for the sake of others in the future, be aware that the same 10a fuse also controls the headlight washer relay and the Rear Defogger relay. Getting to the switch is not easy. First remove the screws that hold the cover plate on the center console and then the screws that hold the complete set of heater controls in place. This was the easy part, but, this heater control unit will not pull out! You have to go to the opposing end of the each of the 3 cable controls and undo each cable up under the dash and unplug each of the 3 electric wire harnesses immediately behind the controls. There is little slack in the wire harnesses and it is tedius, but you can get the wire harnesses removed, but to get to the opposite ends of the cables. You have to remove the lower dash panel on the drivers side to get at the cable on that side and remove the lower duct work cover under the glove box on the passenger side to get at the other 2 cables. When these are all released, now you can cautiously pull the heater controls module outward, I suggest not all the way just about a foot or so, so you don't have to fish all the cables back. In this position you can perform a continuity test on the terminals on the backside of the blower selector switch and AC switch, the continuity diagram is on page 55-5 of the Mitsubushi Montero Manual. To replace the blower selector switch, simply pull on the front knob to remove it and behind it is a plastic nut that holds the switch in, use a 9/16 socket to undo the nut and the switch falls out the backside. I spent days on wild goose chases looking for a short somewhere else, when I wish someone would have said that the blower selector switch actives both positive and negative contacts and that there could be a short in the switch.
Tuesday, January 13th, 2009 AT 2:53 PM