I just bought this car the heat only worked on high or not at all and it was hooked up to a relay. He said that before he added the relay the fan ran 24/7 and that the problem was a module that went out and it common in many GM products. My problem is I can't figure out what its called. I have no clue what part I am looking for but I guess it was originally a $700 part and now you can get it for about $200. So if anyone knows the name of the part and how easy it is to replace it would really help me out

 

have you tried the coolant temp sensor?


if you have a repair manual, and a multi-meter, you can test it. but its only a 10-15 dollar part if not.