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Any time you have multiple functional failures, the first thing to look for is a bad ground. I had similar failures on my 1978 GMC pick-up and the problem turned out to be a ground wire not secured to the bed by the factory. This exact problem would not be the same result as your's, but it could still be a broken or shorted ground somewhere. Very difficult to trouble shoot. As mentioned above, i would first look for rodent chewed wiring.