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2000 C240
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2 Posts
Discussion Starter #1
I am able to select between different vent settings, but the windscreen defrost vent seems to be permanently closed. Anyone else have this problem or any ideas as to what it may be?
 

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95 C280, 89 300E, 94' E320 Coupe, 91' 560SEC
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1,095 Posts
yes, the settings are controlled via vacuum lines that move the flaps with actuators. They have rubber boots that crack over time and cause a vacuum leak. you can tell you have a leak if when you just turn on your car you run to the trunk, open it and slap your ear onto the side right by the light. if you hear a buuuuuzzzz-...buuuuzzzzzzz, sound thats your secondary vacuum pump trying to equalize vacuum due to a leak. it gives up after a min or two or if the leak is bad it blows that huge 40A maxi fuse in the fuse box. i had to replace the one that controls the flap to the feet on the drivers side.
 

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2000 C240
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2 Posts
Discussion Starter #3
That sounds right. Anyone know where the one that controls the defrost is located or how easy it is to access?
 

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1995 C280 (165K mi)
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1,595 Posts
i have problems switching it to the center vents. i sometimes hear an air popping sound behind the dash. could that be a leaking vacuum line? sometimes the center vents will work so i am not sure. i have heard that this center vent issue is a model wide problem.
 

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95 C280, 89 300E, 94' E320 Coupe, 91' 560SEC
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1,095 Posts
the regulator can be check with a multimeter and its rather easy to access from the panel beneath the glove box. Unscrew the Blower motor and the regulator is attached to it. I believe however that the regulator is not the culprit as its purpose is to control how much air comes our not Where It Goes. It sounds like the flap is getting stuck and sometimes. The only comfortable way of servicing the damn things is by removing the dashboard. Not difficult to do. But its something best left for the summer time. You can check all of the actuators with the "mityvac vacuum pump" took a total of 4 hrs to do it. You could do it with out the pump but you would have to lend and ear per say and listen to the actuators.
 
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