124W Fresh Air Doors/ Actuator
 

I have a 91' 300E that blows fresh air through the defrost vents when the climate control is off. When the climiate control is on, I still have air blowing through the defrost vents no matter what selection button I have choosen.

Is this an actuator / servo problem?

The big question is: how much of a job is this to repair/ replace the faulty item, as I am sure it is buried deep behind the dashboard?

Anyone out there ever done this?

Help.

Don

The vacuum element for the defrost flap is mounted on the side of the blower box behind the glove box, which is easy to remove. The default position for the flaps is defrost on, so if the rubber diaphragms in the element are shot the defrost will be open. Pushing the EC or chill buttons should close the defrost flap (although it's a little more complicated than that, which is why it is a two-stage element). The part is $34 or so in Fastlane, a little more at the dealer. You can snap the element out, pry it open (springs and stuff inside) and check to see whether the diaphragms are torn. Easy diagnostic, although look for more, less accesible, elements to fail, too.

Defrost flaps and the 87 SDL
 

Vents allow outside air in even with "O" selected on climate control. I gather from posts that it might be the vacuum element from the exhaust flap. Didn't find Larry Bible's tome on the subject (after a lame 3 minute searching effort). So, ...

Questions:
* Where is that vacuum element on the 87 sdl?
* Might this prob be related to my ailing central locking system?
- locks & defrost vents failed at about the same time
- I've noticed that, since locking sys failed, lock mechanisms in the trunk and two front doors don't have that stiff feeling - key much easier to turn.
- My shop says they're on two separate vacuum systems

Thanks for help.