Here's a curious one: my preglow light and seatbelt light on the dash only work with the driver's seatbelt NOT clicked. I replaced the appropriate fuse, checked the preglow relay (with my eye, that is, to make sure everything was connected), and had initially thought this was a preglow or preglow wiring problem. But it has something to do with the seatbelt...but what?

With the seatbelt not clicked, both lights come on in key position 1, then both go off after a second, when the preglow light should go off—don't know when the seatbelt light should go off...presumably when the seatbelt is clicked?

I'm digging in the manual and Haynes, but haven't found anything yet. It's a 1982 240d manual trans.

Thanks for any ideas.

 

The Haynes 123 manual has wiring digrams; you could perhaps trace them.

However, my wild guess is that the one thing they have in common is the Ignition Switch. It could be that it is about to give up.
At least and Ignition Switch is in the $35-$45 + shipping; range depending on what your source is.

 

If you live in the US and want to own the Factory Service Manual that covers 98% of the whole car you can get it below.
Factory Service Manual CD Set $19.99+$7 shipping
http://www.classictechlit.mbusa.com/...ssicTechLit%29

I paid $53 for mine from Mercedesmanuals before I knew it could be bought direct. Even at more than double the price having it has saved me a bunch of money on the repairs I was able to do myself; so it clearly has paid for itself. And, without having to wait for someone elses advice.

 

Thanks, 9112. I'll look into the factory CDs as soon as I get some cash! I just had the ignition assembly replaced (with a good-looking used one). One other possibility is the seatbelt relay, which I've located, and the "Warning device," which in the Haynes wiring diagram is #14 (p287, for an 82 240d): I'm wondering, though, if these are the same thing? I think they must be.

The warning device (Haynes #14) has

-wires from the driver's seatbelt
-both seatbelt and battery warning lights
-wires to contacts on both front doors
-wire to buzzer

I can't find the warning device under that name, so I'm guessing it must be 0015458232.

I brought it to the mechanic who put in the ignition assembly said he couldn't find any problem, that it would take many shop hours to find it, and that it wasn't major in any case (glow plugs do work). I'm fine with those lights not working; I just want to make sure there's no electrical malfunction that will drain the battery, ruin the alternator, etc.