My rear window defroster works, but it won't stay on. The windown will heat up but it will never stay on for more than 40 seconds. Is there a relay or something that could be messed up? I can defrost the window, but it takes like 20 minutes and 50 pushes of the defrost button....

Thanks.

 

mine does the same thing. if your power seat works and the defrost does work then its not the relay itself (ie the defroster and power driver seat are on the same relay). i was once told that it could be the 30A fuse in the fuse panel going bad but when i changed it it only gave me about 30 more secs of defrost. its like when you first turn it on you may get two or three mins max, but when it cuts off and you turn it back on youre lucky to get 15 secs of defrost! (sound about right) i just think this is another one of GM's design flaws .

 

There is no defroster relay..
There IS a circuit breaker, that has a history of failure, and it can be changed to a 30 amp fuse..
That usually solves the problem of to short a cycle.. [it should stay on about 9 minutes..]
Try a 30 amp fuse in place of the circuit breaker[dash fuse panel]