I think my front interior lights might be haunted - they are set to illuminate when the door opens, and sometimes they do, and sometimes they don’t.

Any ideas?

Upgraded parts from a Rolls Royce Ghost? Don't know if they take their cue from the ambient light sensor but i would expect so.

1 hour ago, gurnardtomcat said:

they are set to illuminate when the door opens, and sometimes they do, and sometimes they don’t.

Any ideas?

Do you only have light problem with one door, or do you have this problem with all the doors ?

The interior light is controlled by the BCM which gets its signal from the door lock switches (same ones that signal if a door is "ajar" and also used for the vehicle alarm system). Its quite possible that if the problem is only with one door then you have a sticky switch. If the problem happens when opening any door it could be a faulty connection with the BCM.

1 hour ago, anon said:

take their cue from the ambient light sensor but i would expect so

That would be a good idea and easy for the manufactures to do (little bit of software code) but in fact the interior lights do not care how bright or dark it is outside, they will come on when the door is opened. Most will 'time out' after about 5 minutes if the door is left open.

Ok, they did on my Mercedes.

Thanks - I’ll try the other doors and see what happens.

Hi There, Try the other doors to see if light comes on and off, If they work perfectly then the door switch

is faulty, Check by opening the door then find the switch and push in and release to see if goes on and off

If it is slow to release then clean with paint spirit then try again. You can also remove switch it is held in 2 ways

either by screw or just clipped in which you can wiggle out. Last resort if all door switches ok might just be bad

contact on bulb.

Thanks - I’ll give this try!

34 minutes ago, Henryge said:

then find the switch and push in and release to see if goes on and off

Hello @Henryge, the days of little buttons /switches for the light have been moved to the history books. Starting sometime in the mid 1990's the switch was incorperated with the door lock and it's used these days to monitor 'Door Ajar' - 'Security Alam' -  'Interior Light'. All these functions are monitored and controlled by the BCM (Body Control Module).