Where were the GM A/C people when MB started to design the ACC systems for their cars in then 70's

Can anyone tell me why some of the vac damper controls have two hoses to them and others only one -- I think I understand the one hose type (vac applied to it and it pulls down to open or close a vent - Correct!)

What about the two hose type!!

Also does anyone know what type is inside the heater box that controls the center vent on a 1988SL. I only have a few pictures that steve from continental was kind enough to post a while back

Is a manual for this available?

I want to get to the bottom of this -- if I can. BECAUSE


If the dash needs to come out to fix this then I want to do other things while I have the dash open -- I do not want to take it into the dealer and pay just to fix the A/C -- I was thinking of making it my winter car project -- what fun


Please help!!

The two chamber actuators are typically for the recirculation and desfrost vents that have open, ajar and closed modes. The rest are open or closed.

Sixto
95 S420
91 300SE
87 300SDL
83 300SD

The whole system is shown in electrical and vacuum drawings on the 107 CD.

__________________
Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician

On the 1985 123 cars, I think the damper controls with two hoses are meant to open when they receive a signal from two different controllers. For example, the side vents are open whenever the system is calling for defrost and whenever the system is calling for air conditioning. It has been a while since I saw a diagram on this, but that is my recollection.

I love both of my Mercedes, but they have the worst ventilation system of any car I have ever ridden in with the possible exception of an early 1960s VW Beetle I used to own. The Mercedes systems are unreliable, complicated, and of general poor design.

I started to take it apart -- I hooked up the center vent control unit to the vac fitting on the recir switch to test it -- IT WORKED -- thank God!

So the problem must be with:

1. defrost unit -- car must have two - I can only see one -- does any one know!!
does it have a shaft connecting the two.

2. the unit where all the vac hoses goes to is bad -- I see some relays on top also -- do not know what they do!

I have an old pushbutton unit - put that in -- no change -- so my pushbutton is OK


Does any one know how I get the service CD that steve talked about