Back again with another puzzler.... this time it's climate control.

Short version:
Climate control blows only hot air.


Extended version:

The climate control system recently went a little hay-wire in that one side of the cabin (the passenger side) would blow cold air while the driver side would blow only recycled cabin air.(ie if it was hot in the cabin, it would blow hot air, if it finally cooled off due to the pass side working, it would blow moderately cool air)... all of this time the compressor would continue to turn and engage just fine.

in recent days the system has ceased to function entirely, blowing only recycled cabin air... mostly hot.

the heat system works fine on the few days when it is required, but I cannot find a fault with the AC. All fuses are good, no faulty wiring, ect.

I do not know the location of the AC Relay to check it. If this makes a difference.

This is a 1998 MB E320 sedan.

help?!?!

 

check the duo valve.

 

would the duo valve keep the compressor from engaging altogether?

That is the case. The duo valve seems to be working correctly. at least I hear <click><click> when plugging and un-plugging it... is there some other way to check this valve?

Is there some other suggestion to troublshoot this problem?

My next step is to un-plug the compressor, and insert my test leads to see if I have voltage at the clutch.