Howto: Duovalve maintainance

television

Always remembered RIP
Joined
Mar 14, 2005
Messages
164,073
Reaction score
367
Age
89
Location
Daventry
Your Mercedes
2002 SL500, 216 CL500, all fully loaded
Alex on the 140 the bronze valves are very loose, they were never fixed.

If you look at the photos in the DIY they were not fixed there either, all of the utubes show them as loose

http://forums.mercedesclub.org.uk/showthread.php?t=25909

In the case of the 140 valves, they get a different problem in that the rubber seals swell up restricting the movement so that there is no hot water passing through.

The 210 valve
163108162_6b048f3a70.jpg

163108159_9f73ed79c7.jpg


A 140 valve
 

Attachments

  • DSC00991.jpg
    DSC00991.jpg
    316.3 KB · Views: 25

whitenemesis

Senior Member
Joined
Dec 21, 2006
Messages
17,978
Reaction score
40
Your Mercedes
CLS55 AMG '05
Image from Alex's link, showing swollen seals...

4.jpg
 

television

Always remembered RIP
Joined
Mar 14, 2005
Messages
164,073
Reaction score
367
Age
89
Location
Daventry
Your Mercedes
2002 SL500, 216 CL500, all fully loaded
Image from Alex's link, showing swollen seals...

4.jpg

Thanks the same as my 140 then, this limits how far the valve can open resulting in a cold car.

I have found an easy way to tell if this is a problem, just ground the center pin and apply 12 volts from the battery to either outside pin and the valve should make a good clonk as it closes, in the case of one where the rubber seals have swollen, it makes a dull thud. Very easy to compare the two sides.

On max heat one can also feel the pulses in the pipes that leave the valve.

There is 1 inlet, and 1 outlet for each side of the car, the 4th pipe is the bypass for when the heater is set to cold, not as Parrots post with 2 in and 2 out.
 

Alex Crow

Senior Member
Joined
Jul 9, 2009
Messages
10,677
Reaction score
47
Location
Super Suffolk
Your Mercedes
W169, W124, w202, W203, KTM 250 EXC, VW T25 camper and a Polo in a pear tree
Thanks for putting up the picture, which clearly shows the brass valves press fitted to the shafts, which is why the upper part cannot be split as our DIY poster had first hoped.

I think the original advice to bench test it was well placed, but still we have no need to suspect it faulty until we see 12v PD across the solenoids and hot air in the car...
 

rodisi

Senior Member
Joined
Jun 30, 2011
Messages
186
Reaction score
3
Location
Germany
Your Mercedes
E220CDI 1999 W210
I think a confusion here is that there are several versions of the duovalve and it's possible that we are talking at cross purposes.

The 'upper bronze valves' are not corroded to the plungers, but press fitted onto them.
Follow my link, read the thread and look at the pictures please.

Also, why as the valve being stripped when we have not seen 0v at the outer pins?

Alex, it is now starting to sink in. I was looking at PoD's photos from a completely different perspective and could not see the similarity between it and mine. He says

5) Obviously there are 4 large pipes into the duovalve assembly. 2 for water heading in, 2 for water heading out. The duovalve splits in two which makes sense if you have a blockage that needs clearing. Its fairly easy to split, there are no retaining plastic lugs, just plastic guides.
and he then proceeds to pick up the upper part from the metal plate and not saying that the upper hose must be disconnected (or did I miss that?). That, together with the video on youtube, I thought that the metal plate is supposed to be lifted.

I've marked the photo you put up of the upper half. I hope I am correct in my markings. I'm also beginning to understand about the upper valves being press fitted to the plungers because on the junk yard one I was working on, I could not budge it - I'm glad I read that before continuing on mine.

Regarding the 0V on the solenoids, with the engine cold and ignition on II I put the controls on max cold and the reading between the middle and both outer pins was zero. I hope that was the corrct way.
 

Attachments

  • upper duo.jpg
    upper duo.jpg
    48.4 KB · Views: 15

Alex Crow

Senior Member
Joined
Jul 9, 2009
Messages
10,677
Reaction score
47
Location
Super Suffolk
Your Mercedes
W169, W124, w202, W203, KTM 250 EXC, VW T25 camper and a Polo in a pear tree
I am not sure that some posters here fully understand, but the valve assembly comprises 4x tapered brass valves that press against 4x flexible seals, which can swell as per my repeatedly posted link.
There are two valves for each zone (left or right), which are operated together, with one opening as the other closes. This allows bypass when no heat required IIRC, possibly to enable water flow through other items such as the washer fluid heater or some such.
In the above pictures we can see the two tapered brass valves that do float, and can be separated from the control shaft.
We can also see, press fitted to the shafts 2x more of the tapered brass valves that cannot easily be pulled off the shafts, and will prevent the silver plate being pulled upwards, as in earlier posts.

Did we even try grounding the outer pins?
That would have been easy to do, with the poster already confirming correct resistance and 12v on the center pin.
Just a wire bared at both ends and held onto the valve outer pins at one end and some earth point or body/engine metal work would have done it.
Or testing with the lid of the socket pulled up (easy to do) would have allowed multimeter access to check the pins it in its fitted running state.

EDIT: Over lapped posting, the above was posted while I was typing.
 
Last edited:

Alex Crow

Senior Member
Joined
Jul 9, 2009
Messages
10,677
Reaction score
47
Location
Super Suffolk
Your Mercedes
W169, W124, w202, W203, KTM 250 EXC, VW T25 camper and a Polo in a pear tree
Regarding the 0V on the solenoids, with the engine cold and ignition on II I put the controls on max cold and the reading between the middle and both outer pins was zero. I hope that was the corrct way.

Assuming you mean the voltage reading was 0v, that points to an electrical fault with the control side, rather than a valve fault.
You need to measure 12v across each valve (12v in center and 0v on outer pins) with the plug connected and engine running to see cold air.
You will find that you can hinge up the lid of the plug, with care, making testing easy enough.
 

Alex Crow

Senior Member
Joined
Jul 9, 2009
Messages
10,677
Reaction score
47
Location
Super Suffolk
Your Mercedes
W169, W124, w202, W203, KTM 250 EXC, VW T25 camper and a Polo in a pear tree
I'm also beginning to understand about the upper valves being press fitted to the plungers because on the junk yard one I was working on, I could not budge it - I'm glad I read that before continuing on mine.

Yes, indeed.

As seen in your posted video, the hollow center of the control shafts, must allow your thin probe to go fully through, and contact the top of the lower 'floating' valve - that will explain what we see there.
 

rodisi

Senior Member
Joined
Jun 30, 2011
Messages
186
Reaction score
3
Location
Germany
Your Mercedes
E220CDI 1999 W210
Let me say that I'm an old man that gets easily confused. I've gone over the entire thread again and here are the quotes regarding voltages.

Basically do you have any voltage on the center pin in the connector, it should be at 12volts. it needs 12 volts to put the valve in the cold mode, this variable voltage comes from the controller and it swings from 0 to 12volt on each outer pin dependent on the controller settings.

This shows that the control unit is not adjusting the voltage, as I said to you, there needs to be zero volts on pins 1 and 3 to get cold air.

To test the voltage from the controller the control have to be set to MAX cold, then that should be no voltage on pins 1 and 3.

And why is the valve even being taken apart?

We need to see 0v on your 'pin3' with hot air in the car before we have reason to doubt the valve - it may well be fine.

I think the original advice to bench test it was well placed, but still we have no need to suspect it faulty until we see 12v PD across the solenoids and hot air in the car...

You need to measure 12v across each valve (12v in center and 0v on outer pins) with the plug connected and engine running to see cold air.
You will find that you can hinge up the lid of the plug, with care, making testing easy enough.

Now, I've removed the casing from the connector to make things easier (and of course put a screw driver down there, which shorted something and I lost most of the lights in the instrument panel and put the radiator fan on full blast :shock: I blew a fuse)
So with engine running, both controllers on 'full cold', Eco on and fan on three the voltage between chassis and pin 1 - 13.8V, pin 3 - 13.8V and pin 2 (centre) swinging between 7 and 11V.

Please confirm that, as you Malcolm and Alex told me, I should leave the duovalve and move on to the centre console. That would mean starting all over again and finding how to get in there.

May I repeat that I do appreciate your patience and time.
 

television

Always remembered RIP
Joined
Mar 14, 2005
Messages
164,073
Reaction score
367
Age
89
Location
Daventry
Your Mercedes
2002 SL500, 216 CL500, all fully loaded
We are all talking 2 different things here. rodisi and myself are not talking about the brass upper valve, we have been talking about the lower ones.

I was wrong in saying that that metal plate should come off, the plastic housing lifts off complete with metal plate and the upper valves as in the picture in the earlier post..

I have taken one apart so that you can see that the rubber boot that seals the whole thing is in a bad way, and will let water into the solenoids, plus it was so swollen the plunger could not move.

No one has taken one down to this point as there is no way back once you have.
 

Attachments

  • DSC00992.jpg
    DSC00992.jpg
    258.7 KB · Views: 33

rodisi

Senior Member
Joined
Jun 30, 2011
Messages
186
Reaction score
3
Location
Germany
Your Mercedes
E220CDI 1999 W210
Is that your extremely clean workbench, Malcolm, or is the wife going to be shouting at you for putting your dirty, greasy car bits on the lovely table?:)
 

television

Always remembered RIP
Joined
Mar 14, 2005
Messages
164,073
Reaction score
367
Age
89
Location
Daventry
Your Mercedes
2002 SL500, 216 CL500, all fully loaded
Is that your extremely clean workbench, Malcolm, or is the wife going to be shouting at you for putting your dirty, greasy car bits on the lovely table?:)

I am ashamed to say its the only corner of my office desk that has a clear patch :(
 

Alex Crow

Senior Member
Joined
Jul 9, 2009
Messages
10,677
Reaction score
47
Location
Super Suffolk
Your Mercedes
W169, W124, w202, W203, KTM 250 EXC, VW T25 camper and a Polo in a pear tree
...So with engine running, both controllers on 'full cold', Eco on and fan on three the voltage between chassis and pin 1 - 13.8V, pin 3 - 13.8V and pin 2 (centre) swinging between 7 and 11V...

That is very hard to understand, it is impossible for the center pin to have a lower voltage than the outside ones, as they get the voltage from the center via the solenoid windings.

The 13.8v on the outer 2x pins will mean open valves and hot air.

What about flickering control panel back lighting with headlights on, as per my earlier suggestion?
 

television

Always remembered RIP
Joined
Mar 14, 2005
Messages
164,073
Reaction score
367
Age
89
Location
Daventry
Your Mercedes
2002 SL500, 216 CL500, all fully loaded
Only an arcing connection / fuse would allow the center pin to go lower in voltage, but spade fuses seldom suffer with this problem.
 

Alex Crow

Senior Member
Joined
Jul 9, 2009
Messages
10,677
Reaction score
47
Location
Super Suffolk
Your Mercedes
W169, W124, w202, W203, KTM 250 EXC, VW T25 camper and a Polo in a pear tree
I think actually Malcolm that this is more likely a testing problem than anything else.
 

rodisi

Senior Member
Joined
Jun 30, 2011
Messages
186
Reaction score
3
Location
Germany
Your Mercedes
E220CDI 1999 W210
That is very hard to understand, it is impossible for the center pin to have a lower voltage than the outside ones, as they get the voltage from the center via the solenoid windings.

The 13.8v on the outer 2x pins will mean open valves and hot air.

What about flickering control panel back lighting with headlights on, as per my earlier suggestion?
I had mentioned in my original post that I noticed the passenger side rotating switch didn't have a light and then noticed the heat problem. The next time I turned the lights on, the light was on and then the next time it was off so I tapped on the console and the light came on so there's definitely something loose there. As for the measurements, I have been using a volt meter for over 40 years so I know what I'm reading. Now I repeat, the voltages where taken from chassis to each of the pins. I agree with you Alex that if the centre pin is supplying the voltage then there's something strange.

I also want to repeat that the centre pin voltage was in constant change both up and down. I'm looking into instructions on opening the control console in the car. I've found an excellent one on youtube, a very slight different console but I think it will do. What I don't know where to find is electrical diagrams.

BTW, I found this manual website has anyone had any experience with it?
 

television

Always remembered RIP
Joined
Mar 14, 2005
Messages
164,073
Reaction score
367
Age
89
Location
Daventry
Your Mercedes
2002 SL500, 216 CL500, all fully loaded
I think actually Malcolm that this is more likely a testing problem than anything else.

A few years back I got so fed up finding good ground points in the cars I made up an 1½ meter negative lead that goes to a real ground point in the engine compartment, the ground points in the cabs are all behind the dash, so inaccessible.
 

Alex Crow

Senior Member
Joined
Jul 9, 2009
Messages
10,677
Reaction score
47
Location
Super Suffolk
Your Mercedes
W169, W124, w202, W203, KTM 250 EXC, VW T25 camper and a Polo in a pear tree
Center pin is supplied on the same circuit as the coolant circulation pump, if fitted, and comes from the control panel as far as I can see.

What voltage do you measure there?

Malcolm's point about making sure of your good ground is sound advice, and might be why the voltage seem to have changed.
But if it really was changing, for sure the outer pin voltages would have been dropping at the same time (obviously you were only measuring one at a time).
If this is the scenario, I will go for dry joints in the control panel.
 


Welwyn Merx Limited is a family run business with genuine passion, dedication and 25 years of experience dealing with Mercedes-Benz and AMG passenger cars.
Tel: 01707 395999www.welwynmerx.uk
Top Bottom