Does anyone have any suggestions on what to look at to solve a jammed on rear window heater. The light comes on and stays on, at first i could turn this back off but the switch no longer makes any difference. Comes on straight after engine started, might go off after a while which i'm assuming is the heater sensor or timer kicking the relay back off.

have replaced the switch - no change

have pulled the fuse - no change

next thought is a faulty relay, still trying to figure out where this is, might be behind glovebox, main dealer didn't know where or what the relay is so not a good start.any suggestions or likely causes? am really hoping it's not a wiring fault.