I have a 1996 Olds Cutlass Supreme and my rear defrost stopped working a few days ago. Of course, it's been below freezing for over a week and there's frost on my windows every morning. With the curve on the back window, it's a pain to scrape! I checked the fuse and it's fine. When I press the button to turn it on, the light still comes on and the timer is still working. What else do I need to check?