W201 hot air out defrost & side vents when AC is on

[Jammin190]

1990 190e 2.6 Recently the AC has started blowing scolding hot air out of the side vents and the defrost vents while the center vents are ice cold. So cold in fact it spits water out from the condensation at times.

Any ideas on what might be causing this?

sounds like the heater valve supply vacuum is intrerrupted, no vacuum equals valve open and full heat at side vents

[Jim Anderson]

Try the defrost button. Thats the one that has all but the water valve vacuum actuator in their no-vacuum state. If any of the vacuum actuators, except the water valve, are leaking you will loose system vacuum and get heat when they are activated.

[Johnhef]

open the hood and look for a black rubber 90 degree curved vacuum connector just under the corner of the windshield on the drivers side. they tend to rip there...

[Jammin190]

OK, we're on the the right track it is definitely a vacuum problem. I put a gauge on the intake manifold with the system off and was around 8. With the system on, sank to 5. I also noticed the "economy" gauge reading close to the red while idling in neutral with the A/C on.
I then removed the main vacuum line from the rear of the intake and plugged the manifold. This left the interior without vacuum feed from the engine. The controls responded in the same fashion. (no response).
I then re attached the vacuum line at the manifold and checked vacuum at the "Y" splitter above the fusebox by the windshield. I also checked the vacuum lines that attached. Surprisingly they are all in good shape and there is ample vacuum at the lines.

I read the post about checking action while the defroster is on, but I am unable to follow. When I push the defrost button the fan goes to high and I get hot air out the vents in the same manner, just more out of the top vent. It seems the side vents are always on, no matter what the combination selected.

So I guess the next questions are;
Where to start looking for a leak?
How many vacuum valve flaps are there?

[MTI]

There are 3 vaccum valves situated around the center console and the only way to get at them is to remove the dashboard.