So ive been having this problem for a while now, i have a manual fan switch, but it doesnt activate the fan when i turn the switch on. Its the same when i hook a direct ground up to the actual wire on the box by the radiator, so i know its not a fan switch wiring issue. Whats weird is when i run the fan with the a/c or the defroster, it runs the low speed fan, and stays on when i shut off the car ad have the manual switch on, and wont go off unless i eather turn the ignition back on or turn off the manual switch.