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A3 (AP) Air Con Fault Help Required

Discussion in 'Air Conditioning' started by Tonyc, Apr 11, 2010.

  1. Tonyc
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    Tonyc New Member

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    [Apr 11, 2010]
    Hi,

    I’ve recently purchased a 2004 A3 (8P), and have a fault with the AC.


    The Econ light is on for most of the time, even with the system in “auto” mode. Checking the owner’s manual confirms that there is a fault with the AC system. But sometimes, the system appears to work, and just the Auto button is illuminated, but the air is not chilled when you go down to the lower temperature settings. Going from Auto, to Econ and back again when the system appears to be working I can’t hear the compressor clutch engaging, nor does the larger electrical fan on the radiator engage.


    I have managed to borrow VAG-Com, and there are no stored fault codes for the HVAC system. I have run through the self tests and they all seen to pass ok.


    I am good at diagnostics/fault fining, but this one is foxing me.


    Any thoughts, guidance, additional tests I can run would be really appreciated.

    Regards
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  3. Staz
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    Staz is a retronaut Staff Member Moderator VCDS Map User

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    [Apr 12, 2010]
    I think you may be misunderstanding what the two buttons actually mean.

    Econ disables the air con system - simple as.

    Auto means that the system will try to maintain the selected temperature using air heated by the heater matrix, cooled by the air con system or simply the temperature of the air coming into the cabin from outside. Auto mode will still work with Econ disabled however it will struggle to maintain a lower temperature of course. The speed of the fan will be adjusted automatically also.

    If you turn auto off, the air coming out of the vents will be one set temperature at the constant speed set by the fans control, basically like a car without climate control.

    I may have misunderstood your actual problem but to test the system turn Auto on, Econ off and turn the temperature control to low. If after a while the air is clearly not being cooled, the Econ button doesn't light, no faults appear the clutch is being engaged as you stated then it's likely that the system needs a service. It's a little more difficult to tell how well it's working when the weather isn't too great however.
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  4. Tonyc
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    Tonyc New Member

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    [Apr 15, 2010]
    Hi Staz,

    I had the system re-gassed yesterday.

    Still not operational. No sound of the compressor clutch engaging when switching Econ on/off, or the larger of the two rad fans coming on.

    I have checked all the fuses and they are OK.

    Just have a nice warm blast in my face, even when the system is set to <19c

    Are there any relays in the control circuit worth checking at all??

    Any other suggestions on what to test greatly appreciated.

    Regards
    #3
  5. NHN
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    NHN Retrofitter - Audi - VW - Skoda - Seat Site Sponsor VCDS Map User

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    [Apr 15, 2010]
    All fuses on side panel & under bonnet I assume?
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  6. Tonyc
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    Tonyc New Member

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    [Apr 15, 2010]
    Hi Yes,

    Both sets inside the car and under the plastic cover in the engine.

    One thing to add, I had to replace the intake manifold flap, as it was jammed open, BUT I did not have any fault codes logged or EML lit. I know from reading other threads that a jammed IMF can blow one of the 10amp fuses (F9 or F10 I believe), but mine were fine. In this case is there another part further up the food chain that has suffered/fried that I need to have a look at??
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  7. Staz
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    Staz is a retronaut Staff Member Moderator VCDS Map User

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    [Apr 15, 2010]
    Weird one this. Nothing works but the car doesn't know that it's not working!

    Have you ever had it that the ECON light is on and pressing the button has no effect?
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  8. Tonyc
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    Tonyc New Member

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    [Apr 15, 2010]
    Hi Staz,

    Yes had that problem, up till yesterday when the system was re-gasssed.

    Can now happly switch Econ on & off but still no chilled air!!!
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  9. Staz
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    Staz is a retronaut Staff Member Moderator VCDS Map User

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    [Apr 15, 2010]
    I see, I was getting confused by your original post.

    I'm not too sure too be honest mate. There have been a few like this in the past (although I don't know if there were VCDS errors) and I just tried looking through old threads. One mentions a 30 amp fuse and another couple had leaks and the system was empty.

    Do you still have access to VCDS? One thing I'd suggest is running the system in Auto mode, Econ off and temp to low and seeing if any codes come up since the regas.

    I'm fairly sure someone had a problem with the fan pack before but it was a long time ago :unsure:
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