Okay, forum members --- the question I have is:

WHY does a 240D manual airbox have a flap cable on the blower speed control ??? I'm considering getting rid of the flap and cable and getting on with my project. The flap is located to the inside of the fresh air flap --- see pics below:

__________________
daw_two
Germantown, TN

Links:
Sold last car --- 05/2012 1984 300D Light Ivory, Red interior
Cluster Needles Paint
New Old Stock (NOS) parts

Past:
3/2008 1986 300SDL "Coda"
04/2010 1965 190D(c) "Ben"
& many more

If you notice on the 240D fan control that there is a quarter turn between off and position 1.

This allows ram air to flow through the system, with no fan operation, between off and 1. Sometimes in mild weather that is all you need.

I suspect if you get rid of that you will get no outside air flow into the system.

__________________
The OM 642/722.9 powered family
Still going strong
2014 ML350 Bluetec (wife's DD)
2013 E350 Bluetec (my DD)

both my kids cars went to junkyard in 2023
2008 ML320 CDI (Older son’s DD) fatal transmission failure, water soaked/fried rear SAM, numerous other issues, just too far gone to save (165k miles)
2008 E320 Bluetec (Younger son's DD) injector failed open and diluted oil with diesel, spun main bearings (240k miles)

1998 E300DT sold to TimFreeh
1987 300TD sold to vstech

The fresh aid flap is controlled by the only vacuum pod on this airbox. This setup has the thumb wheel temperature control on the AC

__________________
daw_two
Germantown, TN

Links:
Sold last car --- 05/2012 1984 300D Light Ivory, Red interior
Cluster Needles Paint
New Old Stock (NOS) parts

Past:
3/2008 1986 300SDL "Coda"
04/2010 1965 190D(c) "Ben"
& many more

I will have to dig into the service manual but my recollection on the 240D is that if the knob was turned all the way off there was no air whatsoever out of the vents. But if you moved off 0 but not yet to 1, where the fan was not yet energized, then air would come out of the vents when the car was moving. That air has to be coming from the outside.

__________________
The OM 642/722.9 powered family
Still going strong
2014 ML350 Bluetec (wife's DD)
2013 E350 Bluetec (my DD)

both my kids cars went to junkyard in 2023
2008 ML320 CDI (Older son’s DD) fatal transmission failure, water soaked/fried rear SAM, numerous other issues, just too far gone to save (165k miles)
2008 E320 Bluetec (Younger son's DD) injector failed open and diluted oil with diesel, spun main bearings (240k miles)

1998 E300DT sold to TimFreeh
1987 300TD sold to vstech

Makes sense --- I'd really appreciate you looking at the service manual!!! I don't really want to cannibalize a good working blower switch nor do I want to compromise functionality.

Also, can you post what "triggers" the fresh air door flap to open & close?

Thanks for your help!!!

__________________
daw_two
Germantown, TN

Links:
Sold last car --- 05/2012 1984 300D Light Ivory, Red interior
Cluster Needles Paint
New Old Stock (NOS) parts

Past:
3/2008 1986 300SDL "Coda"
04/2010 1965 190D(c) "Ben"
& many more

I just recently rebuilt one of these. The flap is controlled by the AC only. Basicly it turns on when the AC wheel is set to MAX. IT;s the same as Max AC in other cars. it recirculates inside air. It only activates at max air though. I found mine worked tons better as far as air control when I replaced the fan switch and put a new cable on and set it properly. (refaoming the flaps and cleaning out the box helped tremendously too. Works like brand new now!

__________________
1978 Mercedes 240D
1981 Mercedes 240D
1982 Mercedes 240D