Heat/Duo Valve problem

[dubadaddy]

1997 E420----No codes coming up.

Ok, I have rebuilt the duo valve and put it all back together, however, I am still blowing luke warm air and no A/C from the center vents. When put on "HI" it seems to blow some warm air out of the side vents only.

This is a CA car with about 160K on it. Granted I have to check the A/C refrigerant level but still trying to get the heater working. I did rebuild the thing per this link.

How I fixed my duovalve (W210), got my heat back and saved myself $250! - PeachParts Mercedes ShopForum

The coils look good with all pieces of electrical connection good.

What else could be happening? Could it be that when I trimmed the broken rubber from the upper O-ring that I am now getting a mixture of radiator fluid from one side of the duo-valve to the other? Thus needing a NEW duo-valve? Doesn't seem possible but.....how can I get heat withing the normal temperature range without going to the "HI" setting?

[RichardM98]

"When put on "HI" it seems to blow some warm air out of the side vents only."


If you have the digital CCU, you should not be getting any hot air out of the center vent. This is by design. Cold air (A/C) yes but hot air no. Sorry I don't have any other suggestions. There is an elaborate test procedure to check the functions of the unit. I don't mean the diagnostic check for compressor function but a different one for air flow.

[daddi]

How high is the engine heat when you have luke warm air coming out.