'89 300E heater not working

Hello,
It finally cooled off enough for me to turn on the heater and I'm getting nothing but cold air. Is the problem more likely to be in the dash control
unit or the heater valve? Any suggestions about how to test either would be greatly appreciated.
Thanks,
Mike
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
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.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
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:

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
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

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Motorsforum.com is a website by car enthusiasts for car enthusiasts. It is not affiliated with any of the car or spare part manufacturers or car dealers discussed here. All logos and trade names are the property of their respective owners.