04 sierra only the high setting(5) will work when I turn the fan on. Is there a relay/ fuse I can change or do I need to take this to the dealer to have it diagnosed?
Typically, when only high speed works, the resistor pack is bad. It looks like this http://198.208.187.182/internet/Part...rtnbr=15-81086 and will be located near the blower motor. Sometimes, the glove box needs to be removed to get at it.