Dome light not turning on when driver's door is opened.
 

In my 1988 300E I am having a problem with my dome light not turning on when I open the driver's door. All the other doors it works fine. I can hear a click from the relay box when I activate the pinswitch for the door. Any ideas where to start. I did a search and found some info on a W126, not sure if the info would apply to mine.

TIA,
Steve

The switch is the likely problem. Pull it out and have a look at it. You can also remove the passenger side's working switch and see it it operates from the driver's side. Sometimes you can clean the pin switches out, sometimes not. I would start by working the switch with my finger fifty times or so while watching the light. Then I would try the pass. side switch.

These are a bit different. Pull the dome lamp switch out, check for power. If you have it, bridge the wires and if the lamp comes on, you've got a bad switch. If you have no power there is a relay that powers the seatbelt warning system and the l/f door switch. Its behind the cluster and really is no fun to replace.


Joe

I tested the switches on the driver's door with a continuity meter and they both seem to work fine. Also, the seatbelt buzzer is working fine when you turn the key. I am getting power I assume because as I said, the light works in other positions and when any of the other doors are open.

Steve

I do not have the solution, but I do have exactly the same problem. Empathy, right?

Door switches are fine. Seatbelt warning operates.

I had the 4 position light ( but without the temp. sensor/grill) in my 300SD, as a P.O. upgrade. Same symptoms,went thru the same diagnostic tree. Found that the IC in the light itself was the cause...replaced light fixture...cured. FWIW.

Thanks joe p!
 

I pulled the dome light and found that there was no power coming up there from the driver's door. So I chased down the seatbelt warning buzzer and pulled it out. I took it apart and there was two places where you could see the solder wasn't making good contact. I tested the relay's circuit with my continuity tester and found it was not complete. Got out a soldering iron and heated up the two open parts, and it works as good as new. It would be tough thing to solve without help from others on this site.

Thanks again,
Steve

P.S. I think older MBs should have a soldering iron in the toolkit in the trunk. ;)

Great news!
So where exactly is this thing located?

It's behind the gauge cluster, to the right. Small box about 1" x 1" by 2". Part number 004-545-07-32. If this goes out, your buzzer will still work, but the seatbelt display up by the dome light (and the dome light itself) won't work when the driver's door is opened.

On my 87 300D, I'm having a similar problem. If the relay is bad, would the seatbelt buzzer ring all of the time when the car is running WITHOUT the seatbelt buckled? I have a constant buzzer and no overhead lights in the upper console.