saw this posted on another site - with no answer and have the EXACT same situation - any ideas?

Mark



... Help Please!!
I have a 1986 420 SEL with 116,000 and the climate control is erratic. Hopefully someone has experienced or heard of this complaint for some possible direction:
(1) When I turn the vehicle climate control on A/C, it takes about 15-20 minutes before it starts to blow cold then at will, it will blow warm or ambient air, then will go back to cold and vice versa.
(2) If I have the button pushed in for dash vents only, the air will blow out of both the defrost and dash vents at will. I did notice that when I am accelerating or at freeway speeds, 90% of the air blows out of the defrost. When I am at idle or stop and go traffic, it blows out of the vents. Is this system on some type of vacuum??
(3) If I start the vehicle when cold (the climate control is off,ie the button "O" is pushed in, the blower still comes on for a few seconds or so at will. I did notice if I push the "O" button again, even though it is pushed in, it will shut off. ...

Item 3 is probably the only sure bet. Because it could also effect 1 and 2 I'll give my opinion on it first.

The pushbutton control is most likely thye cause of item #3 and could easily be the problem in #1 also. Too large of an airgap on the compressor clutch is another answer to #1.

On #2, yes this is vacuum controlled and the relationship between freeway and idle says that either the supply is weak or the leaks in the system are small enough that a huge source overcomes them.

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

Thanks, Steve - I will begin the the process - many thansk for the direction and your time to respond!!!

Mark

Removed the Climate Control Unit (CCU), resoldered the the three pins holding on the wheel potentiometer to the circuit board...WORKS like new!!! Spent in excess of $1000 at dealerships and they could not fix!!! Thanks to this website, about 90 minutes of time - DONE!!