Where do I start looking to see why my rear defroster is not working on my 2002 Chev Cavalier

First check fuse and relays. If none are bad, check wire connections on back window. Then take a good look at the lines in the window, are any cracked or missing sections? If so, they make a repair kit for this issue. Hope this helps.

There is a conection between the front wiring harnes and rear under the carpet drivers side somewhere. This is a known problem and happened to my car. you'll need to ID the defrost wire larger guage, and jump the harnes connection, use **** crimp connector