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  1. #1
    Registered Member One Ring
    Join Date
    Feb 26 2018
    AZ Member #
    414666
    Location
    Ottawa, ON

    Strange AC problem on 04 1.8T wagon

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    I've finally got my car on the road, 3 months after picking it up from the previous owner 'AS-IS'. While all the engine related issues have been fixed, I'm having a hard time figuring out why my AC isn't working.

    When ECON is switched off, the condenser fan starts up and the I believe the compressor kicks in, due to a small momentary dip in the idle. Furthermore, the smaller diameter high-pressure line gets extremely cold just where it enters
    the cabin (to the left of the battery). I haven't been able to read the refrigerant pressure, but pressing in the top-up valve on the return line (also next to the battery) causes refrigerant to spray out. Unfortunately, all that comes out of the vents is ambient temperature air.

    Should the high pressure line be getting cold? My best guess was a leak in the hard line, causing a drop in pressure and resulting evaporation. However, the old soapy water trick didn't reveal a leak, and as previously mentioned, the lines remain pressurized when the car is off.

    Anyone encountered something similar? I'm thinking of looking at the evaporator for blockages but it looks like a pretty big job to get to it.

    Also I should mention that there are no fault codes present.

    Edit: I looked at the pressures and duty cycles when the AC is on, it shows about 0.6 amps at 65% duty cycle, and a pressure of 117 psi. When the econ mode is on (AC off), duty cycle and current is obviously 0 while pressure drops to 87 psi, meaning the refrigerant level is correct. Looks to me like the compressor isn't building enough pressure, should I just go ahead and replace it?
    Last edited by dpeters; 07-10-2018 at 06:54 PM.

  2. #2
    Veteran Member Three Rings a4lownslow's Avatar
    Join Date
    Feb 12 2014
    AZ Member #
    144887
    My Garage
    2007 Audi A4 2.0T
    Location
    Hudson WI

    Start with the basics and hook up a manifold gauge. See what high and low pressure reading are.

    117psi is way to low for high pressure.


    Sent from my iPhone using Audizine

  3. #3
    Registered Member Four Rings EuroxS4's Avatar
    Join Date
    Jan 24 2010
    AZ Member #
    53856
    My Garage
    2003 Atlas Grey A4 Avant 1.8T 6speed manual quattro,2002 GSXR 600
    Location
    Paramus,NJ USA

    at .6 amps I would say its working.If the high side line is getting cold the compressor is running.Can you check the ambient temp displayed in the cluster???Make sure its correct and matches actual temp outside.If not check your ambient temp sensor behind the bumper and G 89 near the fresh air intake.Even if you set the temp to LOW.If the ambient temp sensor says it -40 outside you will never get cold air as the ac head thinks that it will freeze the evaporator due to low temps.I am having a similar issue right now.But its comes and goes.I narrowed it down a a faulty G89.
    VW/Audi Immobilizer removal and immobilizer adapting solutions for any and all VAG Vehicles,Odometer matching, SKC/Pin retrieval services.Located in Northern NJ.For inquries pm for details.

  4. #4
    Registered Member One Ring
    Join Date
    Feb 26 2018
    AZ Member #
    414666
    Location
    Ottawa, ON

    Quote Originally Posted by EuroxS4 View Post
    at .6 amps I would say its working.If the high side line is getting cold the compressor is running.Can you check the ambient temp displayed in the cluster???Make sure its correct and matches actual temp outside.If not check your ambient temp sensor behind the bumper and G 89 near the fresh air intake.Even if you set the temp to LOW.If the ambient temp sensor says it -40 outside you will never get cold air as the ac head thinks that it will freeze the evaporator due to low temps.I am having a similar issue right now.But its comes and goes.I narrowed it down a a faulty G89.
    I checked all temps using the measuring blocks described in the VCDS file, and they all look correct. Also, measuring block 002, 'Compressor shut off criteria' is returning 0 which means that there is no fault condition. My best guess is that the rubber clutch blocks on the compressor pulley are slipping, causing the compressor to not build adequate pressure. The car had a massive oil leak coming from the front crank seal which resulted in the compressor, alternator, etc being coated with oil. I'll see if I can remove the AC pulley and degrease and/or replace the parts.



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