Just today my seat belt warning lamp will not shut off normally. Here is what it does:

Start Engine:
Dome light goes out
Seat belt light flashes continuously

Engine turned off:
Seat belt light goes out
Dome light still out

Open door:
Dome light on
Seat belt light still out

Close door:
Dome light stays on
Seat belt light keeps flashing.

Door switches appear to work OK, they still turn the puddle lamps on and off.

I can turn the dome light off with the manual switch, but the flashing seat belt light follows the same pattern (i.e. only is off after turning the engine off and driver’s door not opened yet).

Fuses OK.

I have the N2/4 control circuit diagram, shown below. Anybody encountered this?

What can I do to prevent my battery from running down other than pull the dome light switch?

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1993 W124 300D 2.5L Turbo, OM602.962
2000 Chevrolet Cavalier, 2.4L DOHC
2002 Ford Explorer, 4.0L SOHC
2005 Toyota Prius, 1.5L

http://www.fuelly.com/sig-us/40601.png

Thank you for the complete symptomatic description. Have not seen your exact problem but that's not unusual, this circuit is so interconnected that it's hard to figure out the failure modes. Three possible culprits: the warning unit N2/4 as in your diagram, the seat belt flashing circuitry in the dome light, and possibly (but less likely) one of the seat belt switches. What is the seat belt status in each of your four modes?

Unfortunately, the only practical way to find a solution is to replace the suspected units and see what happens. I have had failures in both N2/4 and the dome light module.

Jeremy

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"Buster" in the '95

Our all-Diesel family
1996 E300D (W210) . .338,000 miles Wife's car
2005 E320 CDI . . 113,000 miles My car
Santa Rosa population 176,762 (2022)
Total. . . . . . . . . . . . 627,762
"Oh lord won't you buy me a Mercedes Benz."
-- Janis Joplin, October 1, 1970

Thanks Jeremy.

It behaved the same with the belts on or off.

Must be the dome light circuitry. I just pulled the dome switch thinking I would remove the seat belt bulb. I disconnected the dome light plug, reattached it and now things are working as they should, for now. Wierd. Must have "rebooted" the dome light.

I opened and closed the front doors multiple times and the dome light auto/off'd OK and the seat belt light turned off too.

This is a good thing because now I can help my wifey wrap presents ...she was worried I'd be working on my MB all night instead!

__________________
1993 W124 300D 2.5L Turbo, OM602.962
2000 Chevrolet Cavalier, 2.4L DOHC
2002 Ford Explorer, 4.0L SOHC
2005 Toyota Prius, 1.5L

http://www.fuelly.com/sig-us/40601.png

My guess is the dome lamp module is simply bad. It has no connection to the seatbelt switches, just the door switches, constant, and switched power. If the dome light and entry lights are working properly the problem likely is the dome lamp.

-J

__________________
1991 350SDL. 230,000 miles (new motor @ 150,000). Blown head gasket

Tesla Model 3. 205,000 miles. Been to 48 states!
Past: A fleet of VW TDIs.... including a V10,a Dieselgate Passat, and 2 ECOdiesels.
2014 Cadillac ELR
2013 Fiat 500E.

Well, I'll keep an eye on it. Guess I'll start looking around for a replacement in case I need one.

__________________
1993 W124 300D 2.5L Turbo, OM602.962
2000 Chevrolet Cavalier, 2.4L DOHC
2002 Ford Explorer, 4.0L SOHC
2005 Toyota Prius, 1.5L

http://www.fuelly.com/sig-us/40601.png

The dome light would stay on no matter what. That is not proper operation for sure. The timer and logic circuitry for the dome light and door/seat belt inputs are all on the dome/light switch module?

__________________
1993 W124 300D 2.5L Turbo, OM602.962
2000 Chevrolet Cavalier, 2.4L DOHC
2002 Ford Explorer, 4.0L SOHC
2005 Toyota Prius, 1.5L

http://www.fuelly.com/sig-us/40601.png

Yes. The flashing seatbelt warning is 100% independent of the seatbelt buzzer. When working correctly it flashes all the time a front door is open and for a short time thereafter, and for a short time after the key is turned on (which it knows from switched power coming on).

I believe there's a section in the FSM about this. I'll try to dig it up.

-J

__________________
1991 350SDL. 230,000 miles (new motor @ 150,000). Blown head gasket

Tesla Model 3. 205,000 miles. Been to 48 states!
Past: A fleet of VW TDIs.... including a V10,a Dieselgate Passat, and 2 ECOdiesels.
2014 Cadillac ELR
2013 Fiat 500E.

That'll keep the Battery Alive until you can fool with what's wrong.

file:///E:/W124v4.3.2/W124/w124CD2/Program/Chassis/82-0010.pdf

Follow directions in procedure above.

Also the Schematic shows the "Signal" from the Seatbelt lock is sent through
the Instrument Cluster itself to the Dome Light/Seatbelt Warning array.

Attached Thumbnails

 

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'84 300SD sold
124.128

Must be in the dome light assembly. I went to the recycler and got a used one for $10. problem fixed.

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www.jerseyplanning.com
1987 300TD 440K - My car
2005 Jeep Grand Cherokee Laredo 107K - Tim's car
2000 - CLK320 100K - Deb's car
1994 C230 150K - Josh's Car

I have a 1987 300td Wagon and this is almost like my car symptoms CAN SOMEBODY HELP ME the car is off and the Front Door lights Stay on the car is on and the seat belt light Flashes Constantly and the Door lights still on when the car is turned off the Seat belt light goes off but door lights stay on i removed the Bulbs on the Door to keep from running battery down

Have you put the light control switch in the full forward position?

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John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 190D 2.5Turbo
1987 190D 2.5-5SPEED!!!

1987 300TD
1987 300TD
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!

you mean the switch to turn off and on the dome light i have tried it in every position there is ....

I have a 92 300te, the dome light does not work as intended.

Position 4: open or close door "dome" light does not illuminate. Puddle lamps will go on and off.

Positions 1,2,3 work as intended (interior and reading lamp, off, reading lamp)

Seat belt lights are always illuminated.
2 are dimly lit, 1 brighter (lights stay on all the time even if car is shut off)

has anyone run into this issue?