E55 K2 2004 - rear heater problems

[dvb247]

Aircon works fine in the front, all I get out of the rear vents is roasting hot air, my kids think I'm trying to cook them alive???
Any ideas, car under warranty so not real concern, just a pain to get it booked in?

[SSDriver70]

The heater duo valve underneath the windshield cowl area is faulty/sticking. Other common issues when this part is bad is no heat at all from front vents depending which way the valve sticks. Take it in and get it fixed, simple repair.

[ngcatterall]

I have the same issue describe on many of these excellent posts with a sticky duo valve. I have taken all the plastic trim out under the windsheild, but cannot locate anything that looks remotely like a duo valve - any help in locating it would be appreciated - thanks

[LuisRosa]

Same as the previous post. Have no heat on front vents. Any one out there that could tell us how to locate the heater valve (pictures would be a plus) it would be great!! I know in my case I rather do the repair myself.
ThanksMuch
Luis