On my '87 300e the front dome light, & door mounted courtesy light, stopped coming on when I open the door. I have switched both door-mounted pins & bulbs with the passenger side, but the driver's side still is dark & the passenger side works fine. Also, I have switched the dome light unit, but the problem remains. Finally, the driver's sunvisor light doesn't work at all, even though the bulb is good. Could a bad visor contact connection of some sort be the problem? Thanks again for your time.
Richard

Your seatbelt warning relay needs replacement. I've detailed the process here: http://diesel.web1000.com/5/

Since you'll be pulling the instrument cluster, you may as well replace the bulbs. Hopefully this helps you out. The part number is 004-545-07-32

Thanks. But would the relay still be bad even if the buzzer still sounds before I latch the seatbelt?

Yes. Check to see if the buzzer sounds when the door opens and the lights are left on. The dome light operating with respect to the passenger's door but not the driver's door is almost always due to a failure of this relay.

Thanks again, Speedy for your input & guidance.
Richard

Yes, and thanks for the pictures. I am planning on making the same repair after reading your old posts.

Has anyone actually taken this thing apart and discovered it can be easily repaired?

I always delight in fixing things with 'no user-serviceable' parts, but I also do not want to take apart the cluster only to find that Mr. Cheapskate I should have bought a new $50 relay instead.

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1986 300E 5-Speed 240k mi.