Hello,
The dome light does not come on when the front doors are opened. Dom elight does work if I manually turn it on. I have read about people changing there seatbelt relay but they were for different models. I want to make sure the same buying a new SB relay is the fix I am, looking for before I take the plung. Any thoughts or suggestions would be greatly appreciated.
Aquaman

Check the switch on the overhead console to make sure the 'door' position is making contact. The 'door' position is with the switch all the way forward - closest to the windshield. Middle position is ON and the rear position is OFF.
If that all checks out OK look at the door switches.
Does the light come on with any of the doors open?

I don't have any input on the Seat Belt relay, sorrry.

__________________
1991 M-B 560SEL Arctic White/Grey 99,000 Miles
1987 M-B 300SDL Ivory/Palomino 229,000 Miles (sold but never forgotten)
2006 Volvo XC70 Blue/Beige
1999 Porsche Boxster Arena Red/Savanna Beige
1986 Porsche 928S Goldweiss/Brown

I had the same problem with mine and ended up having to replace it. Seems something in the IC board on the light burned up. (probably the part that dims the light when the door is closed).

Anyways, $20 and a 10 mile drive to the wrecking yard and I'm back in business.....now if I could just get that IC board out and test all the components I'd have another spare.

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1984 W123 300D Gone to the wrenchapart
1972 W108 280SE 3.5 (sold but not forgotten)
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Fuzzball,
What is it? The IC board behind the doem light. What type of readings am I looking for on the IC. Are there test points on the IC? The dome light does not come on when the doors are open. The rear door lights come on when the rear doors open, so it is damn dark at night when trying to get into the car. Thanks for the input..

I have the exact same problem on the SDL. I have not had the time to figure it out. The signal from the driver's door goes through an extra device (can't recall).

Randy also had the exact same problem on his.

One of us should keep this thread going until we find and fix it for good.

If the dome light comes on when the passenger's door is opened but not when the driver's door is opened, the seatbelt warning relay is fried. When it goes south, it usually doesn't buzz if the headlights are left on and the driver's door is opened.

That's what I couldn't remember...........the seatbelt warning relay. It's attached to the bracket with the cruise control IIRC?????????

On the W126 it's somewhere above the brake pedal. On the W124 it's behind the instrument cluster.

On the W123 it's the silver box bolted to the parking brake lever bracket, near your left knee. I was able to "repaint" the burned circuits on mine with some liquid stuff from Radio Shack, looks like a felt tip pen with conductive liquid that dries in about 5 minutes.

Of course you checked your fuses?

Thanks
David

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2000 Honda Accord V6 137k miles

1972 300SEL 4.5 98k miles

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LOL, Of course not....
I did not check because I can manually turn on the dome light. The doem does not come on for either the passenger or the driver door. So does that rule out the relay? If the dome comes on when I turn it on manually, does that rule out the fuse? Thanks for the follow up guys.

I've had a problem with the DL switch. Sometimes it works, sometimes not. With either door. I think I'll get a new one, since when I wiggle it around in the position closest to the windshield, with the door open, the light comes on, sometimes. Not always. It seems finicky, and probably a cheap fix.

__________________
DS
2010 CL550 - Heaven help me but it's beautiful
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Las Vegas NV

When I had a fue blow that affected my antenna motor, the dome light would constantly flicker on and off with the door open. You have a different problem but fuses are cheap and easy to check though I don't think yours is a fuse problem. Probably a switch.

Thanks
David

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2000 Honda Accord V6 137k miles

1972 300SEL 4.5 98k miles

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http://electric.articles.mbz.org/126domelight/

Overhauling a W126 Front Interior Light

Now, first off I have to say I havn't actually successfully done this. What I did do was take mine apart, breaking it in the process, then cursing mightily when I realized how simple it was to take it apart properly. Had I done this I would probably have been able to repair my defective one - the time delay circuit had failed causing a short that caused fuse 15 to blow - the one that controls all the interior lights.

Now, my time delay circuit board is in three pieces. I broke it taking it apart, but the life it sacrificed was not in vain; I now know how to take these factory-proclaimed-not-serviceable modules apart and fix them.

The one catch is you have to unsolder the circuit board from the 4 spade connectors you unplugged the wires from. Once you've done that properly you can pull up on the two copper contacts that fit into the plastic body and the whole circuit board - and it's not much bigger than a large postage stamp - will come free.

Don't mess with the switch part. I did and could not for the life of me get it working again - it's not a big rubust thing like the seat switches, it seems to be pretty flimsy actually.

Now that you have the circuit board out you need to test it. It's mostly resisters; there's a capaciter, a solid state relay and a 1455 timer chip, but that's it. In my case the relays was fried and shorted 12V to ground. Nice. So, If I'd been a bit more careful taking it apart I'd be replacing a $2 part right now instead of having to get a hole new unit.

Well, as they say on eBay "my loss is your gain". Maybe you can fix yours now if/when it fails.

Richard Sexton

http://electric.articles.mbz.org/126fuse15/

I have also read that the door switch can be at fault also.

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