Air Conditioning problem in '02 B5.5 1.8T

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  1. #1
    Neutral
    Join Date
    Feb 2004
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    Bethesda, MD
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    Air Conditioning problem in '02 B5.5 1.8T

    A couple weeks ago my AC died on me. Being at 58000 miles I wasn't too surprised, and I headed to the auto parts store to pick up a do-it-yourself recharging kit. Simple enough, right?

    When I hook up the refrigerant canister to the low-side port on the A/C system, the pressure reads 65PSI. According to the refrigerant folks this problem may be an issue with the compressor not starting up, so they recommend pumping in a half can of refrigerant and seeing if the compressor kicks in. I can't tell if the compressor is on, but I sure can tell the AC isn't working!

    Any ideas? I just don't want to end up at the stealership! AAARGGH!

    DrPete

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  3. #2
    PassatWorld Staff
    Join Date
    Jun 2002
    Location
    Albuquerque, 1.8T A
    Posts
    12,267
    You can tell if the compressor is on by whether it engages or not - look at the pulley when the engine is running. The center section of the pulley will be stationary when the compressor is off, spinning with the pulley when the compressor is on.

    If your system is extremely low on or devoid of refrigerant, the compressor will not engage. This is good - it prevents compressor damage.

    You may have to pull the belly pan off and look from underneath to see if the compressor is engaged or not.

  4. #3
    Neutral
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    Oct 2004
    Location
    Augusta, GA
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    141
    You should be able to "see" the compressor being engaged by looking at the gauges. You'll also usually hear the clutch cutting in and out with a slight change in idle characteristics. For instance, if you have 65# of pressure on the low side (without the engine running) and startup the car and A/C.... the low side pressure will go down and the high side will go up (a differential pressure). Most basic recharge kits only include the low side guage I think... but you should still see it. With a low charge.. it's likely you'll see the pressure start at 65#, get sucked down to something less than 25 - 30# at which point your low pressure cutout switch will disengage the A/C clutch. Pressure will recover back up until you clear the low pressure cutout point (40 - 45#?) and then the compressor clutch will kick in to start the process all over again. Once you get above a certain suction pressure then you'll only want to charge with the compressor running otherwise you can actually backflow refrigerant if the can pressure is low and lower than the A/C system suction pressure (with the compressor cycled off). Obviously picking a hot day and high A/C load will help keep the compressor on more and generally higher pressures. Low loads and low tempertures will cause the compressor to cycle anyway.

    In cases where the system A/C pressure starts really low you'll have to jumper the relay contacts to the compressor to get the clutch to engage long enough to get the charge in...... at 65# of suction pressure you shouldn't have to do that.

  5. #4
    3rd Gear
    Join Date
    May 2000
    Location
    Tempe Arizona USA
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    2,395
    Might also consider checking the A/C clutch relay and electrical connections to the clutch... The relay is an inexpensive part...

    -Mark

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