That would depend on the temperature selected. Same for the Bi-level and Economy modes, both of which should supply air via the center vents if the temp selector is in the cool range.

Not true. Consider that the ACC uses heat to make cold air less "cold." "Heated" air is not synonymous with "hot" air.

You resume isn't going to help anyone solve their problem. Neither is misinformation.

Really.....just because my troubleshooting approach is different than yours, its wrong? There are more ways than just mine and yours to approach a problem. And they can all achieve the same result. Some just get there sooner than others.

__________________
Proud owner of ....
1971 280SE W108
1979 300SD W116
1983 300D W123
1975 Ironhead Sportster chopper
1987 GMC 3/4 ton 4X4 Diesel
1989 Honda Civic (Heavily modified)
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Section 609 MVAC Certified
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"He who fights with monsters might take care lest he thereby become a monster. And if you gaze for long into an abyss, the abyss gazes also into you." - Friedrich Nietzsche

Relax before you go to far...



Mercedes Benz uses an integrated CLIMATE CONTROL system = constant balancing of heat/air conditioning to achieve the desired temperature.
This is the only reason for the existence of the mono valve..


This is not a heater with A/C attached as an after thought...

I'd do a quick inspection of the internals on the monovalve. It's easy to remove and can answer questions about the conditions of the rubber seals.

When re-installing, make sure the electrical connections are tight. The collars/sleeves on the plug can get loose and make for a poor connection that results in an open (or intermittent open) valve and heated coolant through the heater core. Be careful that you don't short the 12v line at the monovalve. Someone did this recently and he had to repair the CCU traces. If you're comfortable with your meter and the monovalve pins, you could check to see if one pin has continuous +12V and the other pin has a cycling (or more likely steady due to current temps) connection to ground. Messing this up could short your CCU, so there's a risk there.

Assuming, since you posted it, you've got R12 in the system and your compressor is engaging, I'll go with the fact that your system is probably charged.

But you're also describing poor/incorrect operation of the flaps via the buttons. You may have an electrical problem with the vacuum controls, or more likely a vacuum problem.

The airflow diagrams are available here: Scans of airflow for W123 climate control

Another contributing factor to poor cooling is clogged/dirty heat exchangers, like your condensor - make sure it's clean and not filled with dead butterflies; and your evaporator - you can pull the blower to check that and it's probably dirty, but is also difficult to clean.

"The OP didn't comment if he was getting a little or a LOT of air....a failure would result in a LOT of air."

I am getting a lot of air as in all the air is blowing to the windshield.

Can anyone tell me how many connections there are to the heater core?
I see 3 coolant hoses going into the firewall. Does the heater core has 3 connections?

Thanks.

Pete

Three (3)

So is it 2 in and 1 out?

Thanks.

-pete

Yes.