BMW Repair: Heater Blower Hot only on 1 side of interior, clim control, heater valve

Question
Hi, I have an e38 730i v8 (95) with dual clim' control. I have recently had the heater blower motor repaired (new brushes etc) and a new heater water pump installed. My prob' at the moment is that it is only blowing hot air from the drivers side. There is plenty of air power on both sides which tells me the heater blower motor is working fine but the passenger sides air is cool no matter what the temp is set to. Air distribution for the drivers side is fine (temp just right). Thought maybe there could be a flap inside that's stuck and restricting the hot air for the passenger side or maybe it needs flushing? Do you have any suggestions, tips? Please Help... Andy

Answer
Andy, my disclaimer is that this isn't a U.S. spec car that I have seen first hand. Having said that our 740I's have a pair of heater valves in one assembly above the auxilliary water pump(you mentioned). It has one valve for each side of the dual zone heater core. We most often see the solenoid in the heater valve hanging up not letting new coolant into the core. With a metal object tap on the heater valve bodies to see if the solenoid will loosen and start to let hot coolant into the heater core. The heater core has two inlet hoses and one common outlet hose. Another easy check to tell if this is the issue is to check and see if two inlet hoses are hot. The outlet should be significantly cooler than the two inlet hoses. If you just had coolant work performed then make sure the cooling system is full (check when cold). The M60/M62 V8's cooling system is very hard to bleed the air out of. I don't know about the V8 you have. If that heater valve is hanging up then replace it. At least make sure is it plugged in.
-Evan