another name for a servo
 

i am looking for a part in the parts area of this i was told there is no mono valve on a 79 300d. when i look in the parts for the climate control the only thing that pops up is a mono valve. if there is no mono valve what is the name in full of the part i am looking for

Is this it:

http://www.thepartsbin.com/mercedes-ac-servo.html

i think so i dont really see any part under the alternator or any where on the passenger fire wall that looks like that though does it by chance come out of another part i have a gray box with three sets of wire coming out of the top and two hoses that run into one side and out the other to a round canister 4" in height and about 1 1/2" in diameter with one wire clip on the top there is also another canister type housing the falls halfway in between the firewall. basically half in the engine compartment and half not

I also read the post where someone said it was under the alternator. That's incorrect, at least on mine. It's above and behind the alternator on mine. Craig has posted the correct part and picture. The picture has it on its side. The part is about 10 inches or so tall. You should be able to follow the heater hoses from the vicinity of the thermostat housing to the servo.
It's not on the firewall. The monovalve mounts on the firewall but the servo mounts on the passenger inner fender well towards the front.