Peugeot 308 Wing Mirror Problems

Recently purchased a 2008 308 SW 1.6 diesel but the heated rear window isn't working. The power light comes on when pushed, checked fuse and the wing mirrors heat up so there is power. Has anyone come across this and know what to do?

Heated rear screen not working although there is power up to plug in socket. When the rear screen is plugged in the power drops away. Both heated wing mirrors work fine, all powered by the same switch.

Seems to be low voltage to the rear windscreen (0.16 v, believe it should be around 6v). Switch seems to be working as wing mirrors heat up, no visible breaks in wiring. Earth appears to be good.

A few weeks ago someone bumped my car and ripped my passenger wing mirror casing off. Since then every time I drive the car all of the warning lights appear. I’ve tried turning the car off and on again and it still happens. A friend has t...