A friend has a problem with the 4WD part of the truck. It keeps blowing fuses even tho he doesn't engage the 4x4. He traced the wires, no problem there. Between the 2 of us we can't figure out what the problem could be. Can you give us any help? Just before this happened he was using the truck to spray herbicide on his land. at very slow speed. Is there any way this could have caused the problem?