well if you know the headlight switch has something to do with you need to get a volt meter and start tracing wires i would start with the entire headlight circut if it wont work with the low beams on but it will with the high beams on its probably a short or bad wiring around the switch so start there



Please do your self and any future owners of your car a favor. Do not wire your fan to a switch or to the ignition. Repair it the correct way and it will be one less problem to worry about.