'89 300E heater not working

Start by checking the temperature of the heater hoses... is it warm or hot from the water pump? If not, then heater valve or the aux pump is bad.

It is also possible that the heater core may be plugged by the fix leak thing.

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

Tiger wrote:

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