Why in the world does MB have to have such a complicated an expensive
heater water valve ( either monovalve or duovalve ).  The duovalve is
about $440.Also what is so special about the Blower Regulator that makes
it cost 2-300 dollars. Just replaced the Duo and Regulator on a S320 to
a tune of about 1200 dollars. On my old Cadillacs etc. there was a
simple vacuum valve
that was about $15. It worked well and usually longer than the MB
contraption. No shortage EVER of enough heat. Also no need for an
auxillary water pump unless you just have to have the car stay
warmish for 15 minutes after you turn off the engine (REST mode). It
is all of this complication that makes an out of warranty Mercedes
become an extreme liability. I hate to think what the cost of repair
for the current models will be after warranty. The older Mercedes
pre 1992 were simply better cars and less complicated. Well my 1991
560SEL does have a monovalve and it still works but at least it can be
rebuilt cheaply. Is it really necessary to have a sensor to tell where
the sun is and if someone is in a particular seat for the Climate
Control ( maybe this is BMW or Lexus ) but the same logic applies to the
ultra ultra complicated BMW 745LI. Do people want a gadget or a car.
OK I know the answer.
AL

Well, I rapped on the heater valve a couple of times while the heater was on
and it started working.  Left the heater on for 20 minutes or so and then
turned it on and off sucessfully several times.  Perhaps it just needed some
excercise.

Thanks,

Mike