On my 330d 81 and my 240d 82 lets cold air vent out through the 2 center air vents on the dash just above the climate control, the 2 side vents and the defrost vent. My 300cd only vents from the side and the defrost vents when the a/c is on. I've had it for 2 yrs and thought it was suppose to be that way. With so many of you 300cd owners out there I thought I'd ask, does yours vent from the 2 center vents. If it does which button would control that on the climate control. Which button stops it from venting at the defrost vent. It might help me chase down a problem easier if I have One. Thanks ahead for any help you can give. I put an attachment that shows my climate control to help out.

RAY M

You have a problem in the vacuum elements in the dash. Or a problem with the air control switches behind the AC control panel.

Get a Mityvac and test you elements first. More than likely it is the defroster element that is not closing. Or is leaking. It is tied to the center vent element through hoses.
Drop the diver under dash panel. To locate the defroster element, look on top of the tunnel just inboard of the gas pedal. Test the unit. If bad, replace. If good then lets test the center vent element.

Let us knkow the results.

Dave

__________________
1970 220D, owned 1980-1990
1980 240D, owned 1990-1992
1982 300TD, owned 1992-1993
1986 300SDL, owned 1993-2004
1999 E300, owned 1999-2003
1982 300TD, 213,880mi, owned since Nov 18, 1991- Aug 4, 2010 SOLD
1988 560SL, 100,000mi, owned since 1995
1965 Mustang Fastback Mileage Unknown(My sons)
1983 240D, 176,000mi (My daughers) owned since 2004
2007 Honda Accord EX-L I4 auto, the new daily driver
1985 300D 264,000mi Son's new daily driver.(sold)
2008 Hyundai Tiberon. Daughters new car

Thanks. I just spent a good deal of time. Running down some problems with my 81 300d. my 84 300cd is probably close in locations for all the parts. Now that I know the car should vent from the center I'll go at it. Thank you very much for your time and your response.

Which button is suppose to direct the air flow through the center vents and away from the defrost vent.

Here is the diagram from the manual.

A couple of notes about the chart.
The "Main" air flap is the "outside" air flap that opens the system to outside air. It is inside the evaporator box.
The "Recirculating Air Flap" is just that. it cuts out 80% of the outside air. ( why they have the main and recirc, who knows)
The "Defrost Nozzle Flap" are the 2 defroster vents.
The "Legroom Flap" are the floor vents one on each side of the center console.
Notice, no mention of the side flaps. They are always open.

Dave

If you really want to see where these flaps and elements are located, go here

http://www.peachparts.com/Wikka/W123Evaporator



AC vent flow diagram

Attached Thumbnails

 

__________________
1970 220D, owned 1980-1990
1980 240D, owned 1990-1992
1982 300TD, owned 1992-1993
1986 300SDL, owned 1993-2004
1999 E300, owned 1999-2003
1982 300TD, 213,880mi, owned since Nov 18, 1991- Aug 4, 2010 SOLD
1988 560SL, 100,000mi, owned since 1995
1965 Mustang Fastback Mileage Unknown(My sons)
1983 240D, 176,000mi (My daughers) owned since 2004
2007 Honda Accord EX-L I4 auto, the new daily driver
1985 300D 264,000mi Son's new daily driver.(sold)
2008 Hyundai Tiberon. Daughters new car

According to my '83 owners manual the button with the one white arrow down deflects away from the defrost vent, the button with the white arrows up and down directs to the defrost vent also.

__________________

1983 Mercedes Benz 300D Turbo (Daily Driver)
1979 Mercedes Benz 300CD (Needs Lotsa Work)
1963 Chevrolet C10 Stepside Shortbed (Not Stock)
1999 Chevrolet Silverado Z-71 (Fun to Drive)
2007 Nissan 350Z (Wifes Car - Lucky!)

Thanks all that will help when I start digging into it. RAY M