Dome light dead -- fuse OK, bulb OK, what next? - PeachParts Mercedes-Benz Forum

JSlabotsky · #1 08-06-2003, 02:03 PM

My dome light quit working a couple of weeks ago. Please help me diagnose. Here's what I know so far:

- I just tested the bulb and it works fine
- Checked fuse and it is OK. All other equipment on same circuit works.
- Door switches work, because courtesy lamps in door panels work.

Okay, here's the kicker:

I the light stopped working while I was removing the PO's ancient cell phone. The "brain" was mounted in the passenger footwell under the plastic floor cover. I was very careful not to disturb anything in the area. The installer ran two dedicated lines from the fuse box (presumably one switched, one not). So there is nowhere that the phone seemed to be tied into the wiring harness.

Is there anything located in the passenger footwell area that links to the dome light? Or is this just coincidence.

The map light works fine, only the main roof light has stopped working.

What now???

#2 08-06-2003, 03:49 PM

Have you tried either: a) another bulb; b) checking the socket with a meter to see if you're getting juice to the bulb. As for the circuit, I can't help you there.

JSlabotsky · #3 08-06-2003, 04:21 PM

Well, like I said, I checked the bulb and it works. But, to answer your question, no I haven't tried another bulb in the socket.

When I get home from work I'll check for juice. I was messing with it during my lunch hour today so I thought I'd see if anyone had run into this before.

speedy300Dturbo · #4 08-06-2003, 05:45 PM

Jay, does the dome light operate when you open the passenger side door? It might be the seatbelt warning relay, which is a little black "ice cube" behind the instrument cluster. Part number 004-545-07-32 and kind of a pain in the butt to replace.

JSlabotsky · #5 08-06-2003, 05:55 PM

It doesn't work when either door is open. I saw it quit, and at the time I was on the passenger side with the door open. However, the seat belt warning light does flash, and I do hear a buzzer when I start the car.

Being as it went out while I was working on the cell phone removal, I can't help but wonder if somehow I disturbed something or shorted something out. Again, it would have to be in the passenger footwell area.

speedy300Dturbo · #6 08-06-2003, 07:17 PM

Does the buzzer sound when the lights are on and the driver door is opened?

JSlabotsky · #7 08-07-2003, 12:06 AM

Yes it does. What do I check next?

speedy300Dturbo · #8 08-07-2003, 04:42 AM

Hmm, this is kind of odd. I'd replace the fuse with a new one just to see what happens. Pull the dome light from the roof and check to see if all the brown wires are still grounded. If that fails, I'd pull the door sensors out and check to see if they're getting 12v and steady ground at their respective terminals...

wjm · #9 08-07-2003, 01:44 PM

It doesn't sound like it's the seatbelt warning relay. When that goes, the dome light works with passenger door open but not when driver door is open.

I shorted mine when I took the driver door panel off. Evidently the + and - connectors for the door bottom vanity light touched when I was disconnecting the light. So, BE CAREFUL!

JSlabotsky · #10 08-07-2003, 02:06 PM

WJM - When you shorted it, what happened? Did it just blow the fuse? Or did you have to replace the dome light assembly? I've got a line on a new assembly through a forum member, but not sure if that's what I need. Guess I'll get it and if I don't need it I'll just re-sell.

wjm · #11 08-07-2003, 02:08 PM

When I shorted the 2 wires together, it burnt out the board on the warning "Buzzer" module. Yours seems to work fine according to what you are saying.

The door pin on both front doors are connected to the dome light. I would pull the passenger door pin out (it's very easy, just squeeze the ends together) and check to make sure the wires did not come off.

JSlabotsky · #12 08-07-2003, 08:20 PM

Okay, this is weird. I put the SAME bulb back in that I took out, and now it works. Weird! I took the bulb out to test it and left it out for a day (took it out over lunch time at work). Today when I reassembled to await arrival of my new/used dome light assembly, it started working again.

Now if I can just talk the seller into sending back my Paypal payment. D'oh!