Join Date: Apr 2004
Car: MGZS180,MGZR160,MGF VVC,MG Maestro T16, Rover 111
The interior lights are controlled by the Lucas 5AS alarm ECU using a signal from the micro switch in the door lock. The lights on the mirror can additionally be switched on by the switches on the mirror when the doors are shut.
My guess is that one of the micro switches has failed.