The interior lights on my 1991 240 rarely work if ever.
When they do work, it’s only at times when the fasten seat belt light comes on when I start the car.
This happens maybe once every 7-8 vehicle start events.

All the lights go out together. Exterior lights work fine (except back up lights which have never worked in the time I’ve owned the car). Rotating the dimmer **** doesn’t do anything when the lights are out but it does dim and brighten when the lights do work.

The PO gave me a spare dimmer when I got the car and I swapped it out. The previous dimmer had a very dark spot on the copper part/windings where the dimmer contact was.

Another thing I did notice when the lights used to work was that occasionally I would arrive at my destination and put the car in “P” and it would cause all the lights to go out. This would be remedied by turning all the lights off and then turning them back on.

All the fuses look fine in the fuse box. Where should I should start? Try swapping out the fuse(s)?


Thanks.

 

I assume the warning lights all work? key on, the whole row of warning lights come on, start engine, most/all go out ?

I dunno, but I'd be in there with a volt meter when they aren't working and trace the power around.

Looks like the headlight switch circuit 58 provides power to fuse 16 on a grey wire to the dimmer, so thats the first place I'd check for voltage. Fuse 16 also provides power to the right parking lights, front and rear. the ash tray, seat belt latches are NOT on the dimmer, they get their power from the grey wire that goes into the dimmer.

the dimmer output is a brown wire which goes to all the dimmable interior lights.

 

Thank you for the response. Yep, the dash lights come on and then go off when the car is started.

I’m waiting on amazon to deliver the multimeter. In the mean time, where would be a good ground point? I know the one that’s on the right side of the center console/panel where a whole bunch of ground wires are attached.

Is there a more convenient location to ground?
Also, are there any additional areas that I can check? Reason I ask is, I’m not sure if fuse 16 is the problem. If the corner lights front and back work consistently every time irrespective of whether the inside lights work or not, then fuse 16 wouldn’t be the problem?

 

did you ever get this sorted out? I'm having the same exact issue, same year, same model. completely stumped.

 

The fuse panel should have labels.