W211 Heating Failure - I'm Puzzled; Advice Needed

[E55BOF]

Why would I lie to you?

No gloating involved, just confirmation of what I said.

 

[Mondayo]

I've got an E55 S211, if I'm only getting hot air in the back, does that sound like the duovalve then?
Front is fine but the climate isn't working in the back.

 

[E55BOF]

That sounds like a distribution flap problem to me. A scan with a STAR, or a good aftermarket code reader like an iCarsoft MB 2, should find the fault.