Now it's time to play...Name that Relay!
 

The car: early 1979 240D
The location: under driver’s side lower dash cover on left side
The clue: Not plugged in, but everything but the radio seems to be working.

What does it do?

I'm going to guess and say it's either for the seat belt warning or the warning for leaving the lights on.

Danny

Being that is has the Hella name on it, I venture a guess that it has something to do with either the headlights or fog lights.

Glow plug relay. Early W123 have it under the dash. Later (pencil plugs) it was relocated under the hood.

You sure? Warngerat translates to "warning turn out"

I'm not sure, I'm guessing. My W123 is an '83 now; my '78 is long gone.

That was my thought, but the plugs work just fine. Head and fog lights work too. Now that I think about it I do not remember hearing the seatbelt buzzer in this car. I think we may have a winner! :D

probabaly a buzzer that wouldnt shut off ;)

that is the thingy, duh, it is not fogs, or glow plugs, cuz i saw the same relay under my dash yesterday, and my 115 doesn't have those, i would say that it is your emerg. relay.

Maybe unplug it and see what doesnt work :confused:

It was un-plugged when I got the car. I'm trying to figure out what it does before I plug it back in. :D

it's the spare relay?!? :D

does your windshield wiper works? i'm guessing that is it!?!

Yeah,that would make it much harder,hopefully someone will be able to identify it.Good luck:)

Plug it in, turn your lights on with the door open and starter key out, and see if it buzzes.

Just a thought
 

If it is the original glow plug relay and someone upgraded to the new style under the hood it would stand to reason that it is unused.

Just a thought.

The old 240 engine had loop plugs so I am guessing that the car is using the original relay. I may call up the dealer and have them run the part #. When I have access to the car again next week I will have a fire extinguisher handy and try plugging it in. :D

Is it bolted to the emergency brake bracket? It sure looks like the warning buzzer relay to me (seat belt and key warning):

http://catalog.eautopartscatalog.com/mercedesshop/sophio/wizard.jsp?partner=mercedesshop&clientid=catalog.mercedesshop&baseurl=http://catalog.peachparts.com/&cookieid=1CQ0J3JZ41W21535NT&year=1979&make=MB&model=240-D-002&category=All&part=Seat+Belt+Warning+Relay

Warngerät means warning device.
Five bucks says it's the that annoying buzzer that tells you that you left your lights on, after you pull your keys out of the ignition, and open the door. (It could also do double duty for the seatbelts).

That's the one, it also controls the front dome light time delay on the 83 and later W123s.