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Howto: Duovalve maintainance

Discussion in 'Engine, Drivetrain, Fuel and Exhaust' started by Parrot of Doom, Jun 8, 2006.

  1. Number_Cruncher

    Number_Cruncher Senior Member

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    >>I do not know if a hand drill would have the energy to keep the wire tight enough

    The hand winding machine we use at work makes the bobbin turn faster than you crank the handle - what I'm not sure about is how the interplay between the gearing and the length of the cranking arm compares.
     
  2. bigshineybike

    bigshineybike Member

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    job done

    Thanks for all the above advice.
    I now have heat or cool on both sides of the car.
    I rewound the two coils in the duo valve.
    1000 turns of wire and resoldered to the terminals new o rings and all back on the car.

    I hope there is a phot attached to show my winding jig.
    an old hand cranked drill this helped keep the tension when turning and witht he gearing worked out I only needed to count to 290.

    Now its all working I need to ask,
    How hot do the coils get in normal operation?
    mine are too hot to touch, do I need to do some more fiddling?
     

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  3. Alex Crow

    Alex Crow Senior Member

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    wow! 10/10, go to the top of the class. yes they get very hot. very very very. hence the design flaw that sees so many fail. if you want to do these for people i am sure you could charge £50 a go, no problem.
     
  4. cleverdicky

    cleverdicky Senior Member

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    Just come across this thread. Fantastic.

    reminds me of when I used to make inductors for Speaker cross-overs.
    You can buy a bench top tool for doing this. Seen em on ebay also.
    Used for winding transformers. They have a little arm that moves up an down keeping the tension. Bit like winding a bobin on a sewing machine.
     
  5. Number_Cruncher

    Number_Cruncher Senior Member

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    Yes, we use a similar hand driven machine for the inductors and solenoids we design and build - we've modified it quite a bit to reduce the amount of debris it creates as we use it in a clean room environment, for example, we've made up a set of PTFE gears to replace the original metal ones, PTFE debris in the coils being much more benign than steel debris or, even worse for our application, oil or grease!
     
  6. television

    television Always remembered RIP

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    I hope that you did not get cross over your work, and that it induced you to become happy
     
  7. huggybear

    huggybear Active Member

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    hello there,

    first post on the forum, so please be gentle.

    i bought a w124 250d manual straight 5 a couple of months ago, it has as one would expext a few problems, but the most pressing one is the heater only heats the passenger side, drivers side blows cold. ive replaced the control panel on the dash board with a known good one and result is still the same, so im now looking at the duovalve as the source of the problem. would i be right in saying that if i replaced the valve with a 15mm tee on the feed from the pump unit then connected the two branches to the two 1/2" hoses that are attached to the outlet side of the duovalve then, barring a blocked matrix it should then deliver heat to both parts (ie left and right)?. obviously it would be on constantly but i could fit a gate valve under the bonnet to shut it off untill i can get hold of a replacement duovalve.
    dennis.
     
  8. Dec

    Dec Senior Member

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    That’s what I would do Dennis, it would prove whether the driver side matrix is blocked or not and avoid the need to repair or replace the faulty duo valve for the time being..

    You could also go one step further and put both sides of the heater on to the good passenger side duo valve and block off the bad driver side duo valve…access, space and where exactly you would cut the rubber hose, if that is necessary? would be important.

    This arrangement would leave the duo valves where the are and give you full hot/cold control of both sides through the good passenger side valve while the faulty valve is blocked off.

    Only the passenger side thumb wheel would work for making adjustments to the cabin temperature however the wires at the duo valves plug could be swapped around to give the driver side thumb wheel control instead.
    In theory I think that would work but others may have good arguments why it may not.

    Dec
     
  9. huggybear

    huggybear Active Member

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    thanks for that dec, good idea that, linking up both matrix's to the one good one, i should have thought of that myself being a plumber, (hang my head in shame lol)
    cheers dennis.

    p.s. ill let you know how i go on
     
  10. Dec

    Dec Senior Member

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    One other thing, if you go with your origional idea, if you turn the heater blower dial to 0 then all air into the cabin is cut off so no air, hot or cold , so no need for a gate valve to turn off the heater.

    It might be best to use a plastic tee piece, if brass were used it might not be compatible with the different metals in the cooling system and the chemicals in the coolant.


    Dec
     
  11. huggybear

    huggybear Active Member

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    yes, quite right. i might use 15mm plastic tube tube with "speedfit" plumbing fittings, i'll need 1 x 15mm equal tee 1 x 15mm elbow 1 x 15mm stop end & 4 x 15mm jubilee clips.

    plastic / push fit should be up to the job, ive been using it for almost 20yrs on heating installations and never seen one fail.
    regards dennis
     
  12. rmr1

    rmr1 New Member

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    This very long thread started with Parrot of Doom's excellent description of dismantling and inspecting the Duovalves. The rest of the thread rambles a bit. In my 2000 CLK 320, I think I can test and observe the function of the duovalves whilst sitting in my driver's seat.

    After pressing REST for 5+ count, the left auto control will scroll through various sensor readings (as we all know). Items 3 and 4 on the scroll-through are for left and right heater cores fed by the duovalves. If you press the temperature up and down arrows whilst still within the climate control test mode, you can see the heater core values slowly fluctuate in response to the temperature settings... If the item 3 and 4 values behave appropriately and logically - I would assume the duovalves are working fine and don't need to be dismantled. If this has been described before - I apologise.
     
  13. spock500

    spock500 Senior Member

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    MMmmmm not looking too good, one is stuck fast

    [​IMG]

    [​IMG]
     
  14. slk dude

    slk dude New Member

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    Duo valve slk 230

    Parrot - excellent description on the fix. It worked the 1st time, both sides returned to functioning properly and blowing cold or hot on demand. However, problem returned and one side is blowing hot again. I revisited procedure, no luck. Took the coils out, inspected and noticed corrosion and discoloration inside the plastic yellow wrap. I switched the coils to see if it is just the coil, re-assembled and tested. Now the passenger side is blowing hot and driver side cold. Questions: 1) on the duo valve, which side is driver and which side is passenger? 2) Can the coils be purchased individually, where, or does the whole duo valve assembly need to be replaced ($220+)
    Thanks again for your expertise, looking forward to your response.
    SLK Dude
     
  15. television

    television Always remembered RIP

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    No Parts sold for these, you could wind your own, and not hard to do, they are sold here for ½ of that price
     
  16. slk dude

    slk dude New Member

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    Thanks for the quick turn - do you know which side of the duo valve if driver and which is passenger?
     
  17. television

    television Always remembered RIP

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    You can find this with a volt meter, fully cold setting will read 11volts approx so just set one side to cold and you will have the answer
     
  18. jonclancy

    jonclancy Senior Member

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    Duo Valve Screws

    I have been broiled intermittently by my car and while removing this year's chuffing carbon build up (like lumps of toffee!), I decided to strip the duovalve. It's exactly as per Parrot's excellent write up, but I have a tip or three:

    1. When you replace the screws having split the unit, lubricate them with som silicone grease or such-like. That way, they will not bind when you reinsert them and snap off.

    2. If you do snap off a screw, fear not. Just get a heat gun (or hair-dryer at a push, I suppose) and gently heat the plastic housing. After a few minutes of heating, a pair of pliers will be able to grip and extract the screw end. Don't bother trying without heat. It won't work. Penetrating oil is similarly useless in this instance, too!.

    3. 60mm long M3 screws are available on eBay. In the interim, a 50mm M3.5 accessory screw is readily obtained from B&Q. The top valve-casing hole has enough clearance for the screw body, and there is enough meat in the bottom-casing hole for the screw to grip and do up as tight as you need to be watertight. I would recommend the long M3 screw/nyloc combo to be sure for the long term.

    BTW, my valves looked brand new, so I gave everything a wipe and reassembled. Seems to work fine. I wonder about whether this problem could be caused by oxidised tracks in the heater control wheel assembly itself (assuming that it is a potentiometer).
     
    Last edited: Oct 23, 2012
  19. television

    television Always remembered RIP

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    Sadly this write up does not cover that actual parts that fail, it is where water gets into the solenoids due to the rubber seals deforming, the loose little valves never give a problem, the trouble is in the solenoid part.

    What you can do to wake them up a bit is to apply 12v to the pins, center and out side for each one and you can feel the clonk as the core moves, when the Duo valve is working correctly you can feel the pulse on each output hose, you may find that one is weaker than the other when there are solenoid problems
     
    Last edited: Oct 22, 2012
  20. jonclancy

    jonclancy Senior Member

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    Interesting to see that one of my solenoids had a drop of water in it. I cleaned that out.

    CPC supply various section rubber belts in various sizes. If a seal kit is not avaiable for the duovalve, then this may be a way or refurbing a leaking unit?

    Anyone know roughly how much a new duovalve is from the dealer?
     

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