[Dmacneil144]

I have a 96 c280 and heat always blows out of the passenger dash vent even if I have the AC on full blast. Heat also always blows from the bottom of passenger seat flowing into the back seat. I heard that the duo valve could be the problem. Any extra info or advice would be very helpful before I try to fix the problem myself

 

[glenmore]

My son's 2000 C230K did this and a new duo valve solved the problem. No cold air, just hot air from the vents. Even when the AC was not on, hot air would come out of the vents.

With your AC running check the hi-pressure line, should be ice cold and sweating. If this is not the case, then it might one of many other problems, i.e. compressor, low R134, etc.

I have heard that the duo valve just gets gummed up and a simple cleaning will revive them.

An indie shop diagnosed the problem, so I let them do the repair.

 

[rudedude]

I did an instructional on the dual valve a while back here in the 202 forum.
With pics and everything. Do a search. Type in "dual valve repair" and you will see my thread...