I have just worked out a rat nest of wires in my 72' with only the wipers left. Every thing works fine while sitting still but when I am driving down the road the headlights get dim and flicker. I am fairly sure its not a short, I have replaced all the wires for the head lights. I have tried to replicate road bumps by pulling the wires with the car running and their fine. My question is what would cause them to lose power while the engine is under a load? I have tested and tried everything I can think of. Any other sugg.?