2004 WRX A/C compressor questions
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This is a discussion on 2004 WRX A/C compressor questions within the General Maintenance, Troubleshooting & Accidents. forums, part of the Tech & Modifying & General Repairs category; Hi everyone, I have some questions about how the A/C compressor works, as I think mine is having some problems. ...

  1. #1
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    2004 WRX A/C compressor questions

    Hi everyone,

    I have some questions about how the A/C compressor works, as I think mine is having some problems.

    First off, should the belt on the A/C compressor be spinning even with the AC turned off and the fan speed set to 0? What about if the fan speed is 1 or higher but the A/C is still turned off?

    Also, in the center of the compressor, there's a little triangle shape that spins. Does that also turn on and off depending on if the AC is turned on as well as if the fan speed is something other than 0?

    I have some clunking sounds and an intermittent chirping noise that occurs about every 25 seconds, and I believe it's related to the A/C compressor. But I don't know much about the compressor so I wanted to know if it's acting strange.

    Thanks,

    -J

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  3. #2
    Administrator Trainrex's Avatar
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    Your fan speed has little to do with the AC compressor.

    If your front defogger is on, the compressor will engage.

    If the AC is on, and the fan speed set to at least one, your compressor will engage.

    The actual speed of the inside blower motor (fan) has nothing to do with how hard the compressor works. The compressor has an outer pulley that always spins with the engine. The inner triangle you looked at is the clutch. It is an electromagnet that engages and disengages the compressor according to the freon pressure.

    If you are experiencing a chirp when the clutch engages, odds are your AC belt needs to be tightened, or replaced.

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    Quote Originally Posted by Trainrex View Post
    Your fan speed has little to do with the AC compressor.

    If your front defogger is on, the compressor will engage.

    If the AC is on, and the fan speed set to at least one, your compressor will engage.

    The actual speed of the inside blower motor (fan) has nothing to do with how hard the compressor works. The compressor has an outer pulley that always spins with the engine. The inner triangle you looked at is the clutch. It is an electromagnet that engages and disengages the compressor according to the freon pressure.

    If you are experiencing a chirp when the clutch engages, odds are your AC belt needs to be tightened, or replaced.
    Thanks for the help.

    I never realized that having the defroster on will cause the A/C compressor to engage. I constantly have my defroster on, which could be good reason for the belt's or compressor to be going bad.

    One question though, will the A/C compressor (or the clutch) engage with the defroster on but the fan speed set to 0?

    Also, would a problem with the A/C compressor ever cause a rattling sound to occur? I now understand the chirping sound, but I want to know if this rattling sound is also related.

    Thanks again.

  5. #4
    Registered User NitroNate's Avatar
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    The A/C compressor runs on its own belt with a tensioner pulley. If you hear a metallic or bearing noise sound, it is most likely caused by the idler/tensioner pulley. It's easy to take off and spin it. It'll be pretty obvious even at low speeds if it is bad or going bad.

    The other possibility is the bearing inside the compressor clutch assembly, but this is not as likely to go bad. It's a little harder to get to and has to be pressed out and back in. I don't know if you can buy the clutch assembly separately, but you can buy the clutch bearing.
    2004 Subaru Impreza WRX 2.0L
    2011 Ford Mustang Shelby GT500 5.4L
    2005 Toyota Solara SE 2.4L

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