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Duovalve Removal and cleaning

152038 Views 97 Replies 38 Participants Last post by  Suzie_Tall
Hey, folks.

Since the directions to R&R and clean the duovalve are spread throughout a few threads across this forum I thought it would be useful to put them in one single post that we could sticky for the DIY thread.

Credits to: wood'sbenz, raymond- and netdvn for the following information:

Before starting, here are a few tips:

- BE SURE not to break off the small wiring attached to the gadget.
- BE SURE to pack towels beneath the duovalve to soak up spillage
- BE SURE not to drop screws or parts when removing and installing

The duovalve is located on passenger's side in the engine compartment. It is easy to spot as it has two small cylindrical aluminum cylinders. There are 5 torx (I think t-10) screws holding it together. With the car COLD, remove these torx screw (use a magnetic drive so as not to lose a screw). Leave the electrical connection alone. Once the screws are removed, gently remove the aluminum cap of the duovalve - pulling straight up - you may need to use a thin/flexible putty knife to GENTLY loosen it at first.

(When reinstalling, the two small screws in back side are tight clearance so you can use painter's tape and poke a hole for the screw. Before it's fully tight, tug on the tape and rip it out.)

After you remove the aluminum cap, you'll see two plungers in the lower portion of the valve. Gently remove the plungers, dry and clean them with a clean rag - you can use carb cleaner if they're really funky. Once cleaned, lubricate the lower portion of the plungers with some Vaseline and put everything back together.

(Greg's note re: lube... I haven't done this but I think that plumber's silicone grease would be more effective for lubing the plungers, not petroleum based, thinner so it's less likely to impede actuation of these little things, lasts longer, etc.)

netdvn's pics from the longest AC thread in this forum are seen below. Note that in this case he cleaned the duovalve with it installed in the car. If you're going to do the DIY fix from gt4rcdude then it's probably easier to remove the duovalve (personally I think I would remove it to clean it, less likely to drop things, etc.).




[ADDITIONAL INFORMATION] The 1997 E420 (210.072) duovalve is COMPLETELY different, and cannot be easily dis-assembled for cleaning / repair. The same valve is also used on the 1998-1999 E300 turbodiesels (210.025) and CDI (210.026). More details in this thread:

Thanks again to all who contribute to this forum, it helps so many.

Take care and enjoy the ride,
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My duovalve looks different, where do I lube the plungers, the section inside the springs? Thanks!

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Anyone can give answer to the question where to lube the plungers of 1996 E320 duovalve, the cone, the shaft or the spring? Thanks!

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I managed to do mine today at work. After listening to everyone else I was so careful and knew what to expect I did not loose anything and I did not have to cover the body cracks and crevices. I did however draw blood from my thumb trying to unplug the connector, boy your fingers have to be tiny to reach down in there. After 30 minutes of trying and nursing my injury I then realized that the connector does not have to be unplugged. Here are some pics for future reference so folks can see different views of what it looks like and how the electrical connector does not have to be unplugged.


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Hey, danboy...

You might want to check on the type of coolant in your car... The pic looks shows the looking pretty "greenish" and the correct coolant has a golden/amber hue.

There is only one duovalve, and it regulates engine coolant flow through the heater cores.

Set the temperature control to "LO" on both sides and turn off the AC compressor by pressing the EC button and turn the fan on low. Then measure the air temperature at the dash vents on each side.

Under these conditions, if one side is hotter than the other, the problem lies in the duovalve or the pushbutton unit.
Ok so I cleaned the duovalve, but I'm still getting error code
I haven't checked the diverter flap because I don't know where it is. Plus could someone tell me where is the "firewall."
Did you

run How to Diagnose Air Conditioning Malfunctions |
write down the values and errors and clear the errors?
firewall is the bulkhead that separates the engine bay from the passenger compartment.
:bowdown: ohlord
Well, after cleaning the duovalve, the air still doesn't come out from the right vent as strong and it does from the left vent. Do you think this is an indication of the blower regulator malfunction?
Duo-valve would be indicated when temps

were far apart.Air flow could be a stuck flap.Check your pse.
what's a PSE? and where is it located under my hood
your PSE is under the back seat next to your battery. Here is a pic


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It's normally covered up - the photo is with the cover removed.
thanks guys, the picture is great for identification. So I found it, but when you said "check the PSE," what am I suppose to do when I find this thing? What are the things I'm suppose to check?
I have the same duovalve as you have. I am getting the Eb1416 error code. Did you find out where or how to lubricate the plungers? Did you fix your problem?
texholdem, I have the same duovalve as you have. I am getting the Eb1416 error code. Did you find out where or how to lubricate the plungers? Did you fix your problem?
Last time when my compressor is down, it also showed code b1416
Last time when my compressor is down, it also showed code b1416
Hmm... that should be a b1419.
But now I have 1416, not sure it's new or old. I need Greg's code reader.
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