Hello - sorry for the length of this question, but I thought the detail might help avoid wasting anyone's time by narrowing down the possibilities!
I have a 1997 VW Passat saloon. Recently I noticed that the internal lights (front reading lights and lights above the rear doors) would sometimes randomly turn on and off while driving. The lights would also sometimes activate when locking the car. Also affected are the hazard lights, which also sometimes flash after the car has been locked.
My garage have looked at it a couple of times, and have checked that the circuits under the passenger floor were dry. They replaced a faulty switch in the boot that was not always activating the light (in case a short circuit was activating the lights and alarm system).
The hazards coming on when the car is locked is hard to observe as I can't park it so I can see it all the time. Sometimes the lights activate a few seconds after parking, last night it was a couple of hours later. As far as I can tell, the lights only activate when the interior reading light is set to activate when doors are opened - so far it doesn't seem to happen when the light is switched permanently off (although it's hard to be sure as the problem is intermittent).
The garage say that the interior lights and alarm system are linked via the central locking system (if I understand them correctly). The alarm was news to me - it doesn't have an audible alarm (I don't know if the siren is broken or disabled).
I'd like to know if anyone can think of reasons for these problems? Even if I could prevent the problem by keeping the interior lights off, I am worried that the problem could still be draining the battery or a sign of a more serious issue.
Another recent issue with the car is that the breather pipe was replaced to fix a problem with the engine idling poorly and stalling. Since the repair the idling problem hasn't improved much, but I have been told to give it time to settle down (they had to reset some computer settings during the repair). This is probably not related but thought I should mention it just in case!