Mercedes: Heat blowing only. NO a/c or fan control, mercedes benz club, climate control system

Question
QUESTION: 1985 300SD.  When I turn my A/C on, all I get is very hot air blowing from dashboard.  I can not control fan speed and can not control which vent to let hot air out off. Basically if my air vent is not off all I get is very hot air. Any help would be great

ANSWER: Mander,
It is a possibility that the mono-valve is not operating because it is sticking or the electrical is not being provided properly. On my 86 420SEL it is located in the firewall well. Has two leads to operate the solenoid and several hoses in the side.
You would need to drain some water below the valve and remove the screws to pull the plunger out. It may have gunk on it.
I bought one on ebay a while back. when it arrived and I looked at the location, I knew that I did not want to run the risk of breaking something trying to remove the old valve. I just remove the wires and then the screws and pull out the old unit. I dropped in the new parts and it has worked fine since. I will say that my problem was no heat at all.
The climate control system on my 86 is very complex. As it uses a blending process to mix hot and AC air to create warm air. The fan control is part of the process.
You may want to join the mercedes benz club forum http://www.benzworld.org/forums/  
to see what other possibilities are out there.

Good luck let us know how it turns out.
Rob


---------- FOLLOW-UP ----------

QUESTION: Thanks Rob for your quick response.  After reading your response, I took the wood panel that covers the A/C switches off. I did not do much, I just wanted to see what I was looking at.  I also removed the panel under the steering wheel, just to see what was there too.  After doing this I started the car and tried the A/C. To my surprise the A/C now works at full power, but the heater does not work now and I can not control the A/C unit. Basically the same thing is happening, but now my A/C works. By the way, This is my first Mercedes and I bought this one 7 days ago.

Answer
Mander,
That is a curious turn of events. Your thermostat wheel may have a loose connection or be defective and when  you remove the panel this could have cause it to reverse the process.
By full do you mean blower speed or is this the temperature function?
Rob