Please reread what 'Cletis' posted. Too much current is your problem causing either a thermal breaker to cycle or another device/part to fail including a wiring junction. If the #3 test is correct and you maintain a constant 11.5 volt to the headlights at the switch then the switch is not the problem. Is it possible this thermal breaker is "downstream" of the switch? You might have to 'chase' the problem by using your vom with a sharp pointed lead to probe the wire(s) going to the headlights. When the voltage goes from constant to pulsed, back up toward the sourse and 'zero in'. You also need to look hard at the dimmer switch, you can wire around it with a couple of jumpers if necessary. Good luck.
