W123 wagon dome light issues
 

Hello again! Trying to get the newly purchased '85 300TD in wife-friendly condition (at her request, she *loves* it but we'd both like to iron out a few quirks before it's her daily ride...) and the Becker swap, door lock issues, and trans modulator vacuum-tightness resolution have gone a long way toward this... but...

I can't get the dome light to work. Tried a spare from my old W126 days. Not the unit itself. Test light revealed power and ground are available at two of the wire connections (sorry, can't remember which) so I'd think I could at least get it to light by switching it in one direction or the other. Nope.

I can follow a wiring diagram just fine, but before I tear through the whole car (pin switches, kick panels, etc) is there something *simple* I'm overlooking here?

The rear compartment light works when you operate the dash switch, but not at all by opening the tailgate, and the front light never comes on no matter what.

This bugs me. I've got the ALDA tweaked so the wagon just scoots (LOVE the '85 converter/ 2.88 combo) we're ready to paint the set of hubcaps we found (when I find some steelies, anyone for polished Bundts?) as we both like that look better than Bundts, and I've got a line on paint work to fix the AZ oxidation on the horizontal surfaces... this may be my new favorite Benz!

I just, for safety reasons, want the light to come on and illuminate the inside so my wife can see that the car's empty. And I'm looking pretty foolish here!

Finally a post that I know a little about!

I have an 84 300TD and had an issue with the dome light when I bought it. It wouldn't work at all, but I recently got it sorted out. There are some posts on this forum that will help you out, but the best bet will be to go to a junkyard and pull a couple (because a lot of them don't work) and try them out. I pulled 3 from a junkyard and found one that worked properly.

Another thing you can try is to pull yours apart and look for soldering that is faulty. I pulled mine apart and found one pin that was loose. I resoldered it and it still didn't function correctly, so I trashed it.

You will see inside that there's some pretty complex circuitry in there including a capacitor that will run the dome light for a few seconds after the doors are closed.

What I did.