I have a 06 impala ltz my rear defog doesnt work, the indicator light lights up but no action!!.... I cant find a defog relay anywhere, I thought that may be the problem but nobody has the part?? Any help would be great .... I checked all the wiring and its connected in the back window??

 

Can we move this into Impala Section

 

Relay is under the hood in the fuse box at the right strut tower. Also check the 40amp fuse labelled BATT3. It should have power when the defogger is turned on. If it does have power, then the relay is good. If it doesn't have power the problem is between the fuse and the control head.
If you do have power at the fuse, check for power at the rear window on the purple wire. If you have power there, then the problem is most likely on the other side of the window in the ground circuit. If you don't have power, then there is a broken wire between the window and the fuse