I have a 83 500 SEC(euro) in park it idles between 1400 and 1900 rpm's. According to Chilton's it is the temperature switch or the idle speed control relay. I got a control relay but I can not find where it goes.
Thank you
Brendan Winchell

The control unit should be located behind the engine between the firewall and the windsheild.

Usually if the controller is faulty, the idle speed actuator isn't far behind.

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Benzmac:
Donnie Drummonds
ASE CERTIFIED MASTER AUTO TECHNICIAN
MERCEDES SPECIALIST 11 YRS

I’m not sure if this is applicable to this year of car, as I don’t know exactly when the electronic idle speed control first came into use.

There is (prior to the electronic type system) a temperature sensitive valve that regulates the amount of air going to the engine. It is located towards the front of the engine, on top, with bypass air hoses going to it. These tend to get weak or stick after many years of service.

RTH

Beleive it or not I have both systems on this car. I replaced the temperature valve and the problem persists. I bought a control unit (thank you for the location) and apparently I was sold the wrong one, with the new one on it continues to start itself. I bought it from a german car parts recycling center. They take wrecked mercedes and salvage the good parts and sell them for a more reasonable price. The only problem are all sales are final and it as I said seems not to work right.