duo valve full of fluid? - Mercedes-Benz Forum

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post #1 of 4 (permalink) Old 08-18-2010, 02:22 PM Thread Starter
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duo valve full of fluid?

I have a 2002 Clk320 with air conditioning problems. I opened the duo valve to clean it and it was full of anitfreeze and running all over the place. Is the valve supposed to be like that or do I have a leaky valve. Seams strange to me that it's filled with fluid.
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post #2 of 4 (permalink) Old 08-19-2010, 06:33 AM
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Caveat: I have a 1988 with a monovalve. Assuming the duovalve function is similar, it must be bathed in coolant to do it's job monitoring engine coolant temperature and controlling flow through the heater core.

In other words, normal condition.
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post #3 of 4 (permalink) Old 08-19-2010, 07:46 AM
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Just fyi - the duovalve is not really part of the a/c system. It is part of the coolant system that heats the heat exchanger under control of the a/c system. It will always be full of coolant.

See the coolant circuit for your W208 below. (item 6 is shown but not referenced on the drawing)
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File Type: pdf W208 coolant cct.pdf (170.0 KB, 70 views)
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post #4 of 4 (permalink) Old 08-19-2010, 01:38 PM
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The default stage for a duo-valve is open therefore coolant would flow thru it, it is closed by electrical input from the HVAC controller.
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