Fan Switch : This is a thermo temperature switch designed to turn on and off your cooling fan. This switch may do more than one function in some applications like turning on a high or a low speed fan. The fan switch may be directly hooked to the fan motor, switch on and off a fan relay(s) or give an input signal to a module. Problems with the fan switch can cause serious damage if ignored. An engine can overheat rapidly if a signal to turn a fan on is not being given from a fan switch. Fan switches also can go bad by not giving the proper signal at the proper temperatures. I f you need your fan switch diagnosed or replaced, checkout Guy’s Automotive for all your cooling system and mechanical needs.