I've pasted this here from Tech forum 'cose nobody reads it !

Need a little insight on this problem please..........


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I am going to sell my 1992 300e so I am going to have to fix the low heat output....something I put off while I drove it..

My MB shop book does not cover the symptom as far as I can see....does anyone have an enlightening description of the job to correct the following..

When fully warm, blower runs fine and air volume is okay but the harder/faster the blower runs the cooler the air flow.
New heater valve fitted last year but it changed nothing......if you shut the blower off/low and run the engine for a couple of minutes the heat is there for 10 seconds or so and gradually cools off with the blower turned on again.

Temperature is just above ambient if system on HEAT/MAX/RECIRC'/AUTO.
In the summer it will cool until you need to turn it down/up ?....so the a/c cooling is fine......could this be a flap/flap actuator/vac' problem....and how easy is it to get to them.?
Have cleaned the overhead temp' sensor and suction fan is running.
I ran a water hose through the heater pipes and flow was not restricted.
Aux' pump runs okay.

.......any ideas ?


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