Duo Valve - Repair

[stfallet]

I have a challenge with my duo valve - A0018300784. Interestingly not just on one car.

Situation is that it continuously heats, independent of the temp dial setting. When I tap against it with a small wrench, it closes. But once open again, it is stuck again. Being Swabian, I did contemplate having my son reach out of the window and continuously tap against it. But wife opposed this solution. So I guess I need to repair it.

I assume that descaling the system could be one option. Has anyone tried this successfully?

The other option is to get one of these repair kits. The only thing I'm finding is these aliexpress part kits. Has anyone tried successfully one of these? And idea in regards to the quality?

https://de.aliexpress.com/item/1005...|x_object_id:1005011709925877|_p_origin_prod:


Any other throughts?

thx Stefan

 

[gsxr]

No luck convincing the wife, huh?

I'd start by taking the valve apart to see if any part has failed, or if it just needs a good cleaning. The AliExpress kits (or similar) may be the only option other than buying a used duovalve and hoping it works better (because new is NLA, of course).

 

[stfallet]

This NLA game is really disappointing and worrying. Hard to avoid seeing a limping W124 as prey and to become its predator.

 

[doolar]

There’s a NOS valve with no. 0018303884 for sale here in Sweden. I don’t know if it’ll fit and the price is approx. $800, yikes. But I felt I had to mention it rather than not!

If it were my valve I’d disassemble it like @gsxr says and just do a cleaning and look for any broken parts.

​

 

[dreaming.haze]

Duoventil *erneuert* Mercedes W124 0018303884 Heizungsventil

Biete IM AUSTAUSCH ein komplett überholtes und instandgesetztes Heizungs-Duoventil mit angebauter...,Duoventil *erneuert* Mercedes W124 0018303884 Heizungsventil in Dortmund - Hombruch

www.kleinanzeigen.de

Also an option. Already renewed it seems.

 

[stfallet]

A big thanks to everyone, It is great to see how everyone supports each other.

I'll first try cleaning it and if I need to replace something then use the seals of the AliExpress kit. If that does not work, I guess I have to sneak into the Mercedesmuseum and "borrow" the one from the "Last Build E500 Limited". I mean, how often do they actually use it.....

 

[stfallet]

Just descaled it with coffee machine cleaner (Stole wife's last bottle). Now everything bright and shining. Did polish the moving parts.

I'm intending to lube it with SONAX silicon spray. Any objections or alternative recommendation before I reassemble it?

 

[stfallet]

Re-installed it, but not happy with the result. Maybe I should have waited till my aliexpress kit is here.

But I do have two observations:
1. You don't need to deinstall the complete valve to clean it and replace the seals. unscrewing the top will do.
2. The coils look like they have been used for generations of mercedes cars W201, W126, R129, W210, W202 so I'm tempted to try to use one from a one of these and merge it.

 

[stfallet]

So a few confessions to make and to be made:
1. I was working on my A124.066 and not my W124.036 (I hope I'm forgiven by this forum)
2. I moved a part from my W124.036 to my A124.066 (I hope I'm forgiven by wife and who ever is watching hing from above)

And now to the technical stuff:
1. The duo value was and is perfectly fine. At least now it is descaled and cleaned
2. I noticed that the circulation pump had zero voltage and the left valve had only 3v
3. The right valve was working perfectly.
4 Swapped the control unit from the W124.036 to my A124.066 and now all is working. The control unit seems to be defective

Interesting observations:
1. The A124.066 has a duo valve with integrated circulation pump
2. The W124.036 has only a duo valve the circulation pump is separate (I assume it is the one directly infant of the Control box)

Now I have to check what is wrong with the temperature control unit

Update;
Wife’s comment: “You made a car an organ donor again?!?!”

Update 2:
The temp control unit from the A124.066 that does not work correctly works fine in the W124.036

Why? Why? Why?