interior light won't come on when door opens
 

i need to determine if problem is door switch or light itself. i disconnected light and tried to find a connection that would show power when i opened door. does anyone know which one of the wires powers the light when door is open. light works fine when i push switch.

whitcre,

Does the light work from the manual switch? If it does, its probably the door switch not working. Did you test the bulb?

The door switch completes a ground connection to the light. Ground wires in MB are usually brown but I'm not sure if the wires to the door switches are brown.

BTW, you should always supply the year and model.

P E H

The door switches might be used to ground a relay rather than the bulb/ lamp unit itself. It is also possible that the door switches are used to ground a timer unit/ relay which may also be at fault.

If it does not work from the manual switch I would check the bulb, fuse and manual switch in that order.

If it does work from the manual switch the possibilities are the door switch or the manual switch, or human error by leaving the manual switch in the third position (disable).

I'm not sure what model you have so this is generic information, but if it is the door switch you have two of them and it is highly unlikely that they would both fail simultaneously, so if it lights with one door open, but not the other you have a bad door switch...

I find my manual switch in the disable position from time to time and wonder why the lights don't come on when I open the door...

Good Luck!

If it's a 124 or 201, odds are good that it is a faulty seatbelt buzzer relay. Search on that.

But check the door switches first.