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Howto: Duovalve maintainance

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

  1. Alex Crow

    Alex Crow Senior Member

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    Your Mercedes:
    W169, W124, w202, W203, KTM 250 EXC, VW T25 camper and a Polo in a pear tree
    Pretty much, but it does not regulate the voltage, but switch an earth, giving the 0v.
    When it is open circuit no current will flow and PD = 0v
    When the circuit to earth is made current can flow, and PD = (circa) 12v

    The water flow temperature is regulated by switching the valves on and off at a low frequency, but the valves are essentially supposed to be either fully open or closed.
    Hence open vs closed time will control flow temps.

    One other test you could try is switching the outer pins around in the plug, if the cold side of the car swaps over, that takes you to the control panel, without passing 'GO'.
     
  2. rodisi

    rodisi Senior Member

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    Your Mercedes:
    E220CDI 1999 W210
    It is

    So basically it's either open or ground as opposed to my saying 12V and ground.

    Unfortunately a spanner has been thrown in the works. Today I drove to town. On the way the heater acted as previously stated, one side cold one side hot. On the way back, both sides went cold ARGHHHHH! :mad: My wife was in the car with me and witnessed it so I'm really not mad.

    Last night I decided I was going to check and see what it would be like to get to the control unit so I did up to the point where it was in my hands but saw the difficulty in opening it. As I also saw the price of a new one, I didn't try. I did put it up on the forum in case it hasn't been done before.

    http://forums.mercedesclub.org.uk/showthread.php?t=129509
     
  3. rodisi

    rodisi Senior Member

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    Your Mercedes:
    E220CDI 1999 W210
    OK, I couldn't take the uncertainty any longer so I opened the duovalve, the proper way. As far as I can see there is nothing wrong with it - all clean apart from a couple of little green specs. Photos below show it. So I'm it looks like I may have to learn how to open the control unit. Maybe I should go to the junkyard where I found a similar car and take out the unit.
     

    Attached Files:

  4. television

    television Always remembered RIP

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    Your Mercedes:
    2002 SL500, 216 CL500, all fully loaded
    It is also well known that the switches can get dirty causing a poor contact on the press button control switches, by lifting the top cover some non drying switch cleaner can be squirted in.
     
  5. rodisi

    rodisi Senior Member

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    E220CDI 1999 W210
    I hate leaving things unfinished so I want to say, thanks for all the help - it's working. I have no idea why. After opening and closing the duovalve and unplugging the control unit and plugging it in again, it appears to be working. I've been on two long drives and the heating is working as it should. How long this will last I have no idea but for now I'm leaving it alone. Next headache is replacing the thermostat as I've realised from reading other threads that the 60 degrees the car has been running at, since I've had it is not correct. But that's another thread.:)
     
  6. television

    television Always remembered RIP

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    Your Mercedes:
    2002 SL500, 216 CL500, all fully loaded
    If the engine has only been running at 60c then the car will feel pretty cold what ever the temp is set at.
     
  7. Waynifer

    Waynifer New Member

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    Location:
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    Your Mercedes:
    SLK 200. 2005. 1800cc
    Duo valve.

    Hi.
    After reading lots of threads about this, I can only assume that my duo valve is at fault.
    Cold A/C on drivers side and hot on passengers side regardless of setting.
    I had the A/C system gassed/recharged with no change.
    I have located the duo valve but it's very difficult to get to and I don't think there is enough room to lift the covers off.
    The valve is located forward of the brake servo and the solid pipes go over the top of the duo valve.
    Can I tackle this from another way?
    I don't really want to tamper with the servo system.
    Is there anything I can try to release a possible stuck valve?
    I have a 2005 SLK 200.
    Thanks.

    Wayne.
     
    Last edited: Aug 6, 2014
  8. bob 6600

    bob 6600 Senior Member

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    Your Mercedes:
    Audi S8 V10, S210 E320 CDI (R.I.P.)
    You can try giving it a few taps with a hammer
     
  9. Waynifer

    Waynifer New Member

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    Your Mercedes:
    SLK 200. 2005. 1800cc
    Job done!

    Hi.
    Thanks to Bob, a time consuming and possibly expensive investigation has been avoided.
    I gave the two valve bodies a few taps with a small spanner (that all I could get in the space), tried the air con again.....perfect!
    The two small plungers must have been stuck open.
    I've tried a few times turning the two heater dials up and down and all is working.
    None of this Torx 5 screwdriver milarky and needing hands of a 5 year old to get into spaces.
    Thanks again Bob.

    Waynifer
     
  10. m3gt2

    m3gt2 Senior Member

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    Your Mercedes:
    '68 E220 estate Premium Plus, Command Online with Virtual Cockpit, soft close doors and full ceramic
    Hi, can anyone tell me where they are located on facelift W220 S320CDIs please, got 1 car where driver side is always hot and another where passenger side is always hot! Thanks


    Sent from my iPhone using Tapatalk
     
  11. bob 6600

    bob 6600 Senior Member

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    Your Mercedes:
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    I believe on the W220 it is located near the bulkhead area and is a bit of a pain to get at/out.

    Someone will confirm this for me
     
  12. AdamG

    AdamG Senior Member

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    Your Mercedes:
    S320CDI (2003)
    Yes the duo valve on the w220 is near the bulkhead in the centre.

    It is a bit tricky to get to as the wiper mechanism has to be removed.

    I have recently repaired the auxiliary electric circulation motor followed by stripping and lubing the duo valve due to uncontrolled full heat on the passenger side.
     
  13. roberto230

    roberto230 Member

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    Guys,

    I would appreciate your help as I have now read advice and watched youtube videos for 2 days.
    Finally took a deep breath and took the duovalue apart on the car today. Car is a W124 4 cylinder petrol 2.3 1992.
    Problem is hot air on passenger side and cold on the driver's. When finally opened up I cleared out as much as appeared necessary on the bronze valves and the seatings - mainly dirty rad fluid no solid bits - put all back together and same problem still exists.

    I would like to understand some things before looking at the heater matrix and possibly reverse flushing.

    To assist me undertstanding videos and earlier comments on this site can someone please help by confirming (or otherwise):

    1 Hot water should flow towards the duovalve from the matrix and return to the block via the small pump (having entered the matrix from a single pipe on the passenger (battery) side.
    2. For hot air it is essential to have a closed valve as determined by the 26 degree setting on the internal consule.
    3. Closed valve means the stem controlled by the solenoid is in it highest position i.e not depresses against the spring.
    4. The valve nearest the driver side wing (RHD) controls the matrix providing heat to the driver side vents in the car. I assume this as the higher of the 2 hoses from the matrix as this is colder than the lower hose which is warm.

    Prior to dismantling today - I have tested the electrical connections to the dualvalve and only get a multimeter measurement when temperature settings are in the cold position. When in the cold consule control position and with ignition turned on there is a jolt from both domes when the connector is put into it's correct position by connecting to the 3 pins.

    I don't want to move on from eliminating a problem with the duovalve prematurely but would appreciate advice to make sure I have done as much as can be done before reverse flushing the matrix or looking at temperature sensors.

    Thank you.
     

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