W210 AC Duovalve Questions - PeachParts Mercedes-Benz Forum

shertex · #1 07-10-2014, 04:09 PM

Haha....doesn't take long for a new acquisition to have problems.

On the 99 E300 I just picked up, I am experiencing the following: intermittent warm air (definitely hotter than ambient) coming out of the left front vent and the left rear vent while cold air comes out of the other three front vents and the right rear vent. There is adequate refrigerant in the system. There seems to be no rhyme or reason as to when everything works fine and when it doesn't.

One particular question: if the problem was with the duovalve, would that manifest itself with warm air also coming out of the left center vent...or not necessarily?

I've been reading some threads....I'll read some more...but just wanted to get my exact symptoms out there to see if anyone has any comments.

Thanks.

UPDATE: While it was sitting in driveway blowing warm out of left vent, I used that most precise and scientific of methods: I gave the duovalve a few good WHACKS with some pliers. Shortly thereafter, it was blowing cold! Maybe coincidental...we shall see.

winmutt · #2 07-10-2014, 05:11 PM

'Mericuh

jay_bob · #3 07-10-2014, 08:26 PM

Yup looks like stuck duovalve to me.

Pull parameters 03 and 04, that is your LH and RH heat core temperatures. Hold down REST for 5 seconds, use the left AUTO to change the parameter, the argument is on the right side display in degrees F.

However marginally low refrigerant on these cars manifests itself as the left side getting warm before the right side. Parameter 07 is the refrigerant hi-side pressure in Bar (multiply by 15 for PSI) and 08 is the refrigerant hi-side temp in Deg F.

shertex · #4 07-10-2014, 09:01 PM

On the 98, it was cooling on the right but weak on the left....refrigerant solved the problem. On the 99, it's heated air that's noticeably warmer than ambient and refrigerant is fully charged.

$288 for a duovalve. I know some folks take them apart the clean them...I think I'd rather buy a new one.

jay_bob · #5 07-10-2014, 10:07 PM

It's worth a shot to remove the assembly and clean it out first.

You do not have to remove the hoses nor will you lose more than a couple drops of coolant.

If you pull back the wire bails then you can lift the mechanism off the valve body.

It is simple to remove the tiki drink umbrellas and clean them and reassemble everything.

Just do not do what I did, lose one of the bails under the relay box. Had to take apart the whole thing to retrieve it. Tie some dental floss to each bail so that when it pops off you can save it from the abyss.

TMAllison · #6 07-11-2014, 09:48 PM

Kartek did a write up concerning taking the dou-valve apart and cleaning it IIRC. I usually just gave mine a few good whacks with a rubber coated crescent wrench....when cycling the key didn't work.

shertex · #7 07-12-2014, 12:38 PM

Talked to PO....he had some issues about 5 or 6 years ago, disassembled and reassembled the duovalve, and it worked fine for the remainder of his ownership. I guess I might try the same if my whacking regimen doesn't work.

This video is excellent. https://www.youtube.com/watch?v=8jhPEfLI45s

Kartek's write-up: http://www.peachparts.com/shopforum/tech-help/242566-how-i-fixed-my-duovalve-w210-got-my-heat-back-saved-myself-$250.html