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  #1  
Old 10-18-2008, 07:40 PM
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Question W140 question

Hi, Why do I get extream heat from the two outside vents in all modes, once and a while driving ? The car is a 93 300sd ! Thanks


Last edited by jef d; 10-18-2008 at 08:33 PM.
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Old 10-19-2008, 03:16 AM
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Do a search on Duovavle and one on duo valve. Mine is acting up right now also. I just bit the bullet on a new AC compressor. I'm going to wait a bit before I replace my duovalve assembly.

-Jim
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1995 S350D, Green with black leather interior.
Bought January 2008 w/ 233,xxx miles.
I did 22,000 miles during the first year of ownership.
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Old 10-19-2008, 08:44 AM
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That didnt work, nothing found !
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Old 10-19-2008, 08:11 PM
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Whats a duo valve??
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Old 10-20-2008, 08:23 PM
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bumP
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Old 10-21-2008, 02:13 AM
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A duo valve is the device that takes a single stream of coolant from the water pump and splits is based on input from the left and right ACC temp selectors.

In cooling mode, the valves should close preventing hot coolant from entering the heater cores in the cabin.

Sixto
87 300D
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Old 10-21-2008, 08:07 PM
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where is this valve ?? thanks
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Old 10-21-2008, 11:04 PM
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Try the tech forum. It's not a Diesel question. Shouldn't be too difficult for them

Sixto
87 300D
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  #9  
Old 10-22-2008, 10:49 AM
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The duovalve is on the left side (driver's) of the engine compartment, under the plastic lid that covers most of the fender. It's about 1 foot back from the radiator support.

Are you getting cold air from the central vents when you're getting hot air from the outer vents?

I'd suggest you pull codes from the HVAC system - it should give you an indication of what might be the problem. Here's a quick guide on how to do it:

http://pages.prodigy.net/jforgione/MB_AAC.html

The HVAC system on these 140 chassis cars is complicated, to say the least. Knowing the trouble codes will help track down the offending item.

Post the results of the codes here and I'll do what I can to help...
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Old 10-22-2008, 11:17 AM
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Here's a diagram from AllDataDIY.com (you should consider getting a membership - really helpful):

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