Dear friends,

I'm not familiar with diesel cars. I would like to know the name
and purpose of the key-like button (with the label Adecco attached to it) as shown in the attached image of a 1981 Mercedes 240D.

Thank you very much for your precious help.

Best regards,


Eric

Attached Thumbnails

 

I think that adjusts the cold idle speed; it lets you turn up the idle until the car warms up. I'm 90% sure that this is what it is, since the only car I've owned with one of these, my '77 300D, had one but was not operational.

__________________
Bob Roe
Lehigh Valley PA USA
1973 Olds 88, 1972 MB 280SE, 1978 Datsun 280Z, 1971 Ford T-Bird, 1972 Olds 88, 1983 Nissan Sentra, 1985 Sentra, 1973 230.6, 1990 Acura Integra, 1991 Volvo 940GLE wagon, 1983 300SD, 1984 300SD, 1995 Subaru Legacy L wagon, 2002 Mountaineer, 1991 300TE wagon, 2008 Murano, 2007 R320CDI 4Matic 52K, some Hyundai, 2008 BMW 535xi wagon, all gone... currently
2007 Honda Odyssey Touring, 2014 E350 4matic

Cold idle adjustment should be made while gently pushing the accelerator..... so the knob doesnt have to pull the accelerator linkage.

Turning it all the way counter-clockwise *before* starting dead-cold engine is standard procedure.

Then, you can turn it back clockwise all the way to its "normal" position after the temperature guage registers engine is warming up.