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Old 12-23-2007, 06:29 PM
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Join Date: Jul 2007
Posts: 11
'75 w115 240 A/C Heat Question

I have a 75 Mercedes 240D and I have a questions about the heat and A/C.
My 240D has 2 fans ,one on the lower console and on for the defrost.

I wanted to know which fan is for what. What is the fan on the lower console for? What fan is used for the heat? What fan is used for the A/C?

My defrost fan does not work. It turns on once in a while, but not all the time. My A/C is currently not charged with FREON and doesn't operate. I read something that the A/C has something to do with the vacuum that operates the defrost fan.

Thanks for any help!!!!!!!!!!!!!
1975 W115 240D
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Old 12-23-2007, 11:42 PM
gmog220d's Avatar
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Join Date: Apr 2006
Location: Cottonwood Heights, Utah
Posts: 580

Hey King,

I've got a '73 220D, W115 - same system most likely.

The in-dash fan is used for heat, de-frost, and for moving fresh air into the car. To change where this air goes you use the two blue slides on the control panel. You can send air to the floor, up the wind shield, and/or out the dash vents. Using the slides in the control panel in combo with the vent slides you can come up with various ratios of heated vs. fresh air coming into the car through the various vents.

The fan in the console is for AC only. If your system is working properly it will come on when you turn the AC on, and the in-dash fan will shut down. Vacuum is used to move flaps in the system to "connect" the various vents to the AC system (while disconnecting them from the fresh air intake). And like in "fresh air" mode, you can use the control panel slides to direct the cooled air through the various vents (defogging the windshield vs. blowing at you). The air for cooling is drawn into the system from inside the car, through the sides of the console, I think.

You can allow fresh air in at any time by opening the central vent on the dash, with the top-most slider.

I'm not sure if you can run AC and heat together, since fan speed between the two motors is controlled by a single switch.

Hope this helps!

I lack an owners' manual, and this is what I've figured out so far in my car. I have not been able to experiment with the AC since mine does not work, yet! ;-)
- Greg -
1974 240 Diesel
1996 E300
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Old 12-24-2007, 11:38 AM
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Join Date: Jul 2007
Posts: 11
Thanks a lot for the help!!!!!

I will try running one at a time and see what happens.

Thanks again
1975 W115 240D
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Old 12-24-2007, 12:16 PM
michael cole's Avatar
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Join Date: Apr 2002
Location: waterloo ontario
Posts: 730
if your defrost fan is showing some signs of life get it on life support may just require some bearing lubrication.i beleive you can get at it for lubrication purposes by removing the chrome intake vent below the windshield.even with that removed you will probably have to use some kind of flexible tube to aim the oil precisely upon the bearings.the alternative to this is RandR.not a fun job considering the console and heater core/evaporator must be removed to get at it
michael cole 1980 300SD gone now but not forgotten,87tdt,90 300te 4matic 95 e320 wagon
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