installed later in the winter after all the coldest weather, so did not need to use the heater until the beginning of the next winter. Had tested upon install and it worked. the next winter nothing-it was securely mounted and maybe 5,000 miles were put on the truck between installing and the next attempt to use it. Oh- and the warranty is only for 90 days. pure JUNK. will not be buying a KAT"s brand anything; just need to find something to replace it now...