I've got an electrical problem on my latest acquisition, an '82 300TD. The seat-belt-warning light stays on ALL the time. If the battery is connected, it is glowing red. Any insight? Tried searching, just another post with no responses....

Thanks,
Jay.

There should be an electrical line underneath the driver's seat leading to the seatbelt, and somewhere along there under the seat there's a plug connection. If you don't really care about your seat belt warning light (I mean, you know whether or not you're wearing your seat belt, and if you don't then you shouldn't be driving anyways) then you could just leave it like that.

__________________
"I would rather be ashes than dust!
I would rather that my spark should burn out in a brillaint blaze
than it should be stifled by dryrot.
I would rather be a superb meteor,
every atom of me in magnificent glow,
than a sleepy and permanent planet.
The proper function of man is to live, not to exist.
I shall not waste my days in trying to prolong them.
I shall use my time."

-Jack London 1876-1916

1983 300CDT (running WVO since 12/05)
1981 300SD (parts car)

Your warning module is malfunctioning.
Located under the drivers dash is a 2 inch by 3 inch metal box. This is the " seat belt warning relay.

http://catalog.eautopartscatalog.com/mercedesshop/sophio/wizard.jsp?partner=mercedesshop&clientid=catalog.mercedesshop&baseurl=http://catalog.peachparts.com/&cookieid=1JR0Q2C3E1JT04Y81H&year=1982&make=MB&model=300-TDT-001&category=P&part=Seat+Belt+Warning+Relay

Check a couple of other things. The fuel gauge reserve light should com on when the key is on but the engine is not started. If it does not, this goes thru the same relay.
does the buzzer work for the seat belt warning light when you turn the key on. Head lights left on warning.
Many of these items are separate circuits in the relay so some may work and others are bad. Mine had the reserve light inop but everything else worked.

This is the unit that the light goes thru.

Dave

__________________
1970 220D, owned 1980-1990
1980 240D, owned 1990-1992
1982 300TD, owned 1992-1993
1986 300SDL, owned 1993-2004
1999 E300, owned 1999-2003
1982 300TD, 213,880mi, owned since Nov 18, 1991- Aug 4, 2010 SOLD
1988 560SL, 100,000mi, owned since 1995
1965 Mustang Fastback Mileage Unknown(My sons)
1983 240D, 176,000mi (My daughers) owned since 2004
2007 Honda Accord EX-L I4 auto, the new daily driver
1985 300D 264,000mi Son's new daily driver.(sold)
2008 Hyundai Tiberon. Daughters new car

Not always true. I believe it was a factory upgrade/build change on 300xx models after Dec of 82. Before that, it won't come on with 4+ gallons in the tank.

Much like the timed dome light on 83-85 models.

It will come on no matter what amount of fuel is in the tank. The light is illuminated by the warning system relay during the initial key turning as a test form the light.

This information is for an 82 300TD only, just like mine.

Dave

__________________
1970 220D, owned 1980-1990
1980 240D, owned 1990-1992
1982 300TD, owned 1992-1993
1986 300SDL, owned 1993-2004
1999 E300, owned 1999-2003
1982 300TD, 213,880mi, owned since Nov 18, 1991- Aug 4, 2010 SOLD
1988 560SL, 100,000mi, owned since 1995
1965 Mustang Fastback Mileage Unknown(My sons)
1983 240D, 176,000mi (My daughers) owned since 2004
2007 Honda Accord EX-L I4 auto, the new daily driver
1985 300D 264,000mi Son's new daily driver.(sold)
2008 Hyundai Tiberon. Daughters new car

Not to sound ungrateful, but can you be a bit more specific r.e. the location of this relay? I've got a parts car, so I'll try pulling the unit from it before buying a new one.... THANKS to all for the fast replies. Still have to get the engine back into this thing, so it may be a couple weeks before I get around to chasing this down.

Jay.

A Bosch part number, maybe???

Jay.

Pull the driver under dash panel. Located just above the parking brake pedal assembly on the left wall is an aluminum box. This is your warning relay.

http://img.eautopartscatalog.com/live/P206470204STR.JPG

and

http://catalog.eautopartscatalog.com/mercedesshop/sophio/wizard.jsp?partner=mercedesshop&clientid=catalog.mercedesshop&baseurl=http://catalog.peachparts.com/&cookieid=1JV0R797I1JV0R7DPT&year=1982&make=MB&model=300-TDT-001&category=All&part=Seat+Belt+Warning+Relay

unplug and unbolt the unit and swap it with the other one.

Dave

__________________
1970 220D, owned 1980-1990
1980 240D, owned 1990-1992
1982 300TD, owned 1992-1993
1986 300SDL, owned 1993-2004
1999 E300, owned 1999-2003
1982 300TD, 213,880mi, owned since Nov 18, 1991- Aug 4, 2010 SOLD
1988 560SL, 100,000mi, owned since 1995
1965 Mustang Fastback Mileage Unknown(My sons)
1983 240D, 176,000mi (My daughers) owned since 2004
2007 Honda Accord EX-L I4 auto, the new daily driver
1985 300D 264,000mi Son's new daily driver.(sold)
2008 Hyundai Tiberon. Daughters new car

Killer! Wasn't sure if it was that one, or the one behind the instrument cluster.... Thank you!

Jay.

I am having the exact same problem of seat belt warning buzzer staying on. Is all of this info true for a '75 240d as well as the '82? If I just take out the relay, will I be disabling other important functions? This will be the third relay I'll replace in my car: turn signal ($48)and rear defrost ($54). At prices like that I would be happy to just not be notified of my slothful ways.

The buzzer relay on my 83 240D wasn't working either. I took it apart and found the burned circuit. I was able to fix it with some "paint-on" type contact stuff I found at Radio Shack. I didn't know if it would work, but had nothing to lose by trying.

My light stopped working when i cut the cable to the seatbelt buckle. The original buckle stopped working and i replaced it with a buckle from a 85 sel that i got from a junkyard and it didnt have the cable on the buckle so i had to cut the one from my 83SD and just mounted the new buckle in the original spot and hasnt turned on after that. and the buzz went away too. but thats a good thing for me the buzz ticks me on bad mornings.