In chasing down vacuum leaks in the climate control system, it seems the majority of the vacuum leaks associated with the climate control are coming from the servo unit itself (black box under the hood). I have a handful of lines that won't hold vacuum. Some do. I can post which lines hold and which one don't if it makes any difference as I have it written down.

All tests were done with the car off and vacuum pulled at the line connections on the inner fender near the battery. Some immediately dropped to zero, some dropped and held at 2-3 and some held vacuum.

I'm sure this is not how it is supposed to operate but I do not know for certain. Does this indicate the servo unit is not good?

I really haven't driven the car too much since acquiring it last fall as I have been going through systems getting them 100% operational before putting it on the road. The climate control does respond to changes in the switches and heat does come if I press defrost. That is about all the further I've gotten with testing operation of the unit.

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2009 ML320 Bluetec
1985 300CD
1981 300TD

Past Mercedes
1979 300TD
1982 300TD
2000 E320 4Matic Wagon
1998 E430
1984 300SD
1980 300SD

Not sure of the answer to your question, but I did provide a link to the online troubleshooting manual for a servo a few years ago. If you search on my username and servo manual, I think it should show up.

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

Here is the manual, I had it saved.

1971 Imperial & Chrysler Auto-Temp II Service Book (Session 281) from Master Technician Service Conference


Charlie

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there were three HP ratings on the OM616...

1) Not much power
2) Even less power
3) Not nearly enough power!! 240D w/auto

Anyone that thinks a 240D is slow drives too fast.

80 240D Naturally Exasperated, 4-Spd 388k DD 150mph spedo 3:58 Diff

We are advised to NOT judge ALL Muslims by the actions of a few lunatics, but we are encouraged to judge ALL gun owners by the actions of a few lunatics. Funny how that works

Here is some more stuff:

https://s3.amazonaws.com/sspublicweb/mercedes/Mercedes+116+Climate+Control+Service+Manual.pdf

https://s3.amazonaws.com/sspublicweb/mercedes/83-604+climate+vacuum+diagrams.pdf

https://s3.amazonaws.com/sspublicweb/mercedes/w116-vacuum-climate.png


Thanks to sshanky for the info!

__________________
My occupational hazard bein'
my occupation's just not around...
1980 300SD
1980 300SD

So if I am understanding the servos function correctly, it is to take a constant vacuum supply from the engine and then direct it to the necessary pods and blower to cause the correct function to happen?

If I am thinking about this correctly then when the blower is "parked" as described in the literature, there will be "open" vacuum circuits in the servo that won't hold vacuum when tested with the MityVac. Thus my vacuum tests on the servo are irrelevant in testing for leaks?

Do I sound correct?

__________________
2009 ML320 Bluetec
1985 300CD
1981 300TD

Past Mercedes
1979 300TD
1982 300TD
2000 E320 4Matic Wagon
1998 E430
1984 300SD
1980 300SD

It has a little electric "servo" motor inside it that drives some clockwork gears that do 3 things. It drives a vacuum switch that changes which vents have air coming out via vacuum pods that actuate flaps in the dash. It also controls the blower speeds and opens/closes a water valve at the base.

There are some pics of mine disassembled here:

http://www.peachparts.com/shopforum/diesel-discussion/304961-its-heater-season-acc-fun-2.html

__________________
My occupational hazard bein'
my occupation's just not around...
1980 300SD
1980 300SD