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Help, heater either hot or cold!! W203

Discussion in 'Electrics, Vacuum, Ignition and ECU' started by philiggy, Oct 27, 2017.

  1. philiggy

    philiggy Active Member

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    Your Mercedes:
    c200 CDI 2006
    Hi all

    havent been on here for ages.
    Just bought a 2006 c200CDI

    The heater is eithe red hot or cold....its terrible, cant find antthing on it and its making car unusable

    Cheers
    Phil
     
  2. bembo449

    bembo449 Senior Member

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    Your Mercedes:
    w221 320cdi , r170 23k , range rover vogue , insignia vxr , shitron dispatch
    hi phil , so its not pressurising the water system at all ?
     
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  3. AMGeed

    AMGeed Senior Member

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    Your Mercedes:
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    Get your duo valve (heater control valve) checked.
    I had similar symptoms and mine looked like this on removal
    [​IMG]
     
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  4. OP
    philiggy

    philiggy Active Member

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    Its all fine just had thermostat replaced,,,,where is duo valve situated?
     
  5. OP
    philiggy

    philiggy Active Member

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    No I dont think so
     
  6. AMGeed

    AMGeed Senior Member

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    Your Mercedes:
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    Should be under the master cylinder on the drivers side bulkhead. The part isn't expensive £30 odd but its an awkward job to do.
    BTW, this is only an opinion and please confirm with an indy/your garage before deciding to replace this valve.
     
  7. OP
    philiggy

    philiggy Active Member

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    apparently mine doesnt have a duo valve!
     
  8. OP
    philiggy

    philiggy Active Member

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    apparently mine doesnt have a duo valve!
     
  9. AMGeed

    AMGeed Senior Member

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    OK.........I thought all W203's had them??

    Oh well, back to the drawing board:(
     
  10. andy.alias

    andy.alias Member

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    Your Mercedes:
    2005 C220 CDI Avantgarde SE Auto
    Hi Philiggy, did you ever fix this?
     
  11. alexanderfoti

    alexanderfoti MBO Forum Supporter Authorised Forum Supporter

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    Your Mercedes:
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    Yes, no duovalve on the W203's. Heat/cooling is controlled by flaps.

    You can try normalising the flaps by holding Windscreen defrost and recirc buttons until the lights flash.
     
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  12. andy.alias

    andy.alias Member

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    Tried that, made no difference, I have read that it could be the sensor, but I’m not sure where it is, some say the roof light cluster and some say the controll dials..
     
  13. alexanderfoti

    alexanderfoti MBO Forum Supporter Authorised Forum Supporter

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    You need to plug it into diagnostics and compare the values from both.
     
  14. Oldspanners

    Oldspanners Senior Member

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    C CLASS 2004 C180
    Do you have any clicking noises coming from around the heater controls on switching the ignition on or off.
    I had this problem and it turned out to be a heater flap control motor but can also be a cracked plastic operating arm.
     
  15. andy.alias

    andy.alias Member

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    No ticking noises, I might try a punt on a new light fitting, only a tenner on eBay.
     

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