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.

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84 300td (Yes, a wagon)
"The Golden Dragon"
195k, 2nd owner
Lives in Redmond, WA