Question about 2000 Mercedes-Benz C-Class

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My heater in the Mercedes c240 1999 car is not working well. One side of the heater (left hand side is ok) but the right hand side keeps on blowing out hot air even when it is on the cold setting. Any ideas? Also, the engine fan (cooling fan) keeps coming on and it seems to be draining the battery. When I pull out the fuse to this cooling fan, the coolant sensor light stays on and car seems to overheat somewhat. Could this have anythiing to do with the heater blowing hot air? Thanks!

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  • inna2010 Oct 03, 2009

    Thank you for your kind help. I will look into this and see if this could be causing the problem. I will try to keep you all updated as to how it went and whether this resolved it or not.


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The control valve unit behind the dash either broke or stuck. the car has two set of control valves, one for passenger and on for the driver. It common for the unit to fail on all cars some has better luck than others. inside of the valves made out of rubber, over time if it not move regularly it can seized from heat and it get stuck and the motor may have a hard time turning and adjust the valves itself. the only way to get to it and work on it, the dash has to come apart. the part may be cheap if it need it, the bad part is time consuming getting to it and its all mechanic nightmare and the labor will get you. The fan keep coming on, you may have to change the thermostat switch sensor, it could be faulty and not sensing correct temperature causing the fan to stay running. at the same time I would go ahead and have the thermostat it self change, you will have replace that soon or later and you don't want the car leaving you stranded and overheating. by running the heater believe it or not, it also help cool down the the engine a bit. hope that help some

Posted on Sep 30, 2009

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