Annoying "beep, beep, beep, beep" and flashing "bulb out" warning on dash. Scroll through "Check" switch and it says brake, reversing and indicator lights not working in rear offside light cluster. Very dangerous if turning right at night. Taken light cluster off and checked for bad connections, but none. The tail light in same cluster still works. I'm thinking a bad earth somewhere. Haynes don't do a manual for A6 so no wiring diagrams to go off. I'm a sparky by trade, but not auto elecs. Any ideas anyone please.