Q: Interior lights don't work when doors are opened

Hey there, thanks for writing in about your 1990 Mercedes-Benz 300D. Typically there are a couple of different options in the interior light switches. There is usually an option to turn them on manually, or to have them come on automatically when a door is opened. Although, this may sound obvious, often times this switch is in an incorrect position. I would double check to be sure the switch is in the "auto" position before digging too deep into this. If you are still having problems and would like some help, a certified pro from YourMechanic can come to your car’s location to inspect the interior lights for any electrical issues that may need repair.