Climate Control Servo removal Auto Temp II AC 1980 300D - PeachParts Mercedes-Benz Forum

rhodes2010 · #1 03-11-2013, 12:45 PM

I know this topic is off-topic to the purest who wants their car original.
But I finally dove in and removed the under hood servo, the amplifier behind the glove box, and disconnected the vacuum line harness going to the servo.

Behind the panel in the dash disconnected the 4 vacuum operated electrical switches and the 4 electrically operated vacuum switches.

My goal:

1. Control the fan manually, Off 1 2 3 speeds.
2. Activate heat (open hot water line, turn on pump, activate needed vacuum pods).
3. Activate AC (turn on compressor, activate vacuum pods).

My original design was to create three fused circuits with three electrical switches.
The fan was simple enough, control the fan manually.
The heat and AC involve electricity and vacuum, so these each needed
a electrically controlled vacuum switch that would control the required vent pods.

The original idea was going to completely bypass the center console panel and interact with the various fan, heating , cooling parts directly.
Like any cheap manually operated car.

It turned out that I was able to use the original panel to control my vacuum pods and fan speed and AC compressor.
So it is much cleaner then I had thought it would be.

Where it is now:
After starting the car I need a switch to cut all power to the cabin fan/blower.
If I turn this switch on the fan blows on low (even in the off position).
Lo is the same speed. Hi and bi-level move to a higher speed.
So I basically have a two speed fan.

Testing the backside of the climate control panel I determined which buttons activate which vacuum lines and connected the pods directly to get
floor on bi-level and dash air on Lo and Hi.
Defrost override still works (it always bypassed amp and servo).

I took my power for the fan from the blue wire on the back of the climate control panel.

Using the AC Compressor switch I simply ran 12v to it and ran that to the compressor.

My center vents were already clamped open permanently so I can control
vent air by simply closing or opening dash vents.

So far I have set the stage to now connect or disconnect pods as needed to
get the airflow I want.

My next goal is to find a 12 volt water valve to replace the manual one
where the servo was removed. Right now I have the manually operated valve
that is well documented on this forum for doing wintertime heat.

BACKGROUND:
I have owned this car since 1984 (second owner) and have always kept it factory original and working 100 percent. Two Auto Temp II servos (this one is the aluminum one), two amplifiers, two AC compressors. Recently replaced the climate control panel after the old one leaked vacuum.

I owned (and sold) the very rare Climate Control test equipment shown in the Mercedes Benz service manual for diagnosing the climate control system.
Still have the original MB manuals on the complete climate control system.
And have the Chrysler version provided by the Imperial group.

I would rather purchase a 1981 or newer MB without the ACC Servo than
own one of these. Seriously.

NOTE TO THE PUREST:
After owning this car 29 years and getting too old for some of this my
changing out the factory system is a last ditch effort before most likely
getting rid of this car.

Where I live it gets below 40 in the winter, and over 100 in the summer.
We like our cars to heat and cool when needed.
For years I had thought about what it would take to simplify the system
to provide basic comfort and finally tried it.
The other $500 option was the replacement system for the servo
but it still relied on so much of the original design I just did not want another
short term solution.

Flame suit on, sure you folks think I have broken some cardinal rule or am too lazy.
But this was a lot of work and it just might end up being a solution.