I was assured that when I bought a hot rod radiator and el. encased fan I needed the Derale controller #16778 to hold my new 350ci box. Runs cool as a cucumber! (NOT THE CASE) The fan came on once and never came on again almost melting the engine. I hope the fried water pump is the only thing I have to replace!. I tried adjusting the temperature screw but it made no difference. I agree, don't waste your money on this controller.