A/C 1980 300d stopped working
 

My a/c stopped today. Everything was fine until I switched over to defrost. Then switched back to low cool. Would not blow cold. Next day only defrost comes on. No other switches activate anything. I have read up on the forum but everybody has a little different problem than I seem to have. I checked fuse. Is this the CCU contact points failing? Maybe need new CCU (junkyard) THanks in advance for responses. I truly enjoy this forum. 1980 300D.

Help! Hot in Texas
 

Sure could use some help on this one. It is really about to get hot here in Dallas area. I will start on this tonight. Got a long trip planned for Tuesday. I've got to get a/c on.

Defrost works, no other buttons. Fuse ok. 1980 300D

Paul

Could be a bad servo or CCU. My 82 does not have the servo. Someone with servo experience will chime in.

Does the compressor clutch engage?

a/c
 

Compressor does engage. Yes.

Ok, that is a good thing. Do a search for climate control servo.

update a/c 1980 300d
 

Just wanted to update with regards to my a/c problem on 1980 300d. I replaced a/c servo with junkyard find and that fixed my heat to cold problem. Now I can dial in heat or have cold. This is a good thing.

The last remaining problem is that pushbuttons only work when I give the foot pedel a little more trottle. I know that vacuum increases when I do this causing the buttons selected to activate pods. Definitely have a leak.
I have tested all pods and there all good now. I replace one. How do you test switches? Yellow, green, and brass looking ones? I vac on them and hear them click and they hold vac. Is that good enough?

The part that confuses me about this system is the controlled leaks. So, when testing with mityvac you really got to know when your testing an area that should leak down. Make any sense? Should green line at engine leak at all? Should it hold for 5 minutes? Lost here! Car shuts down and door locks work.

When I mityvac the green line at engine I hold no vacuum. I can hear hissing at the pushbuttons when I vac the green line. I figure that the buttons need to be replaced. The part at MB is $140. I have another set of junkyard buttons that do the same thing.

Well, I guess I am officially sick and tired of thinking about this climate control thing. 2 weeks and counting. I really would like to put back center console soon.
Any comments will be much appreciated.

try these guys
 

I bought a rebuilt CCU from these guys and exchanged my old one. It's reasonably priced and way more reliable than taking your chances with a junkyard version. They require your old CCU in exchange. Can't say what the price is now, but about five years ago it was $140ish.

They also do cruise control module rebuilds.

http://www.programainc.com/