I am having some issues I cannot figure out on my 78 gmc. When I turn on the head lights my gauges go weird. The volt gauge goes bottomed out to the negative, my temp gauge maxes out, as does my fuel gauge. If I move the dimmer switch the gauges move with it. I cleaned all the connections for the head lights as well as there ground wires and no change. I am lost on what to do. Could a bad light switch be causing all this? Any help would be great before I just take the truck to the dump. S.O.S!!!