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Old 01-23-2005, 01:31 PM
400E 400E is offline
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Join Date: Jun 2001
Location: Omaha, NE
Posts: 962
Quote:
Originally Posted by mtburton
The car only allows for fresh air to come in so I know it is not a circulation problem. The owners manual for the entire defrost system is one page and it simply says to press the defrost button and it will adjust automatically.

Any other ideas?
I would bet you dollars to donuts that this is indeed a circulation problem (unless, as Manny suggests, you've got too much interior humidity from wet carpets, etc., or your air intake at the end of the hood is clogged with snow and ice). I would also bet you that your car does indeed have the capacity to recirculate inside air.

On my car, at least, the AC is cut off at ambient temps below about 40F, and in fact in most winter conditions you don't need the AC to keep the humidity level down in the cabin, especially when it's really cold out -- the outside air's relative humidity will be very low at low ambient temps, and so when it's warmed up to cabin temp, the relative humidity will be extremely low.

I only know W124s, but on those, the recirc switch automatically goes off after about 10 minutes when outside temps are low, to prevent interior fogging. Don't know about your car's climate control, however.

On older MBs, the vacuum motor which controls the flap which determines the mixture of inside/outside air can and do fail, which can produce the symptoms you're describing.
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Steve
'93 400E
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