I had trouble getting the high to work on mine, I was like only getting like 11 volts on high. Someone was in there cutting and splicing and rewiring ,It was a mess under there. I spent 10 or 12 hours and never could find the problem, so I just put a toggle switch on the dash and ran a wire directly to the fan from a circuit that's shuts off with the ignition, problem solved, I never used anything but high anyway. And now it's easier to go from off to high, I don't have to go through low and medium. You could do the same thing but put the switch between the fan and the factory switch and use it to completely shut it off.