Insignia rear window heating issue

I had a similar problem with my old Renault Megane, although it was the front window that wouldn't defrost properly. Did you check the fuses related to the rear window heating? Sometimes it's just a simple blown fuse.

I had a look at the fuses, and they seem to be fine. Is there anything else that might be interfering with the rear window heating?

Okay, if the fuses are good, then it could be a problem with the heating element itself or the wiring. Honestly, without proper diagnostic tools, it's hard to pinpoint. Given the symptoms, it does sound like a power supply issue, though. Best bet is probably to take it to a workshop.

Understood. I've taken it to a workshop, and they confirmed it was indeed related to the battery, which was heavily discharged. They replaced it and the rear window heating is now functioning correctly. The repair cost 290€. Appreciate your help!