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  1. #1
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    Loud Whine from AC Unit after running

    Hi the past couple of years and the issue is usually present when there is a minimal temperature differential between outside and inside (example: outside 79, inside 74 cooling to 73) though it has occurred when there's a larger difference. Everything is cooling well, but shortly after the condenser turns off (within a min or two) a high pitched whine/whistle starts and usually gets louder over the first 5 mins or so. You can hear the whine inside the house downstairs at the furnace it's quite loud though it can also be heard out at the condenser. It's a loud, constant whine/whistle. If I kick the unit back on by lowering the temp after a few mins it goes up in pitch for a second and then stops - about 50% of the time if I cycle it off right away again it won't come back or it will be much quieter.

    I have a youtube video of the sound if it's helpful, but I'm in newbie "jail" still - this is only my first post

    I had a "professional" from a local company observe the issue once during a proactive check last year, but frankly he was just a young kid who basically said he'd never heard anything like that before and shrugged his shoulders after saying "pressures are good, it cools well, seems fine to me."

    My plan is to call a place out to diagnose more, but on the off chance I can't reproduce the issue I'm wondering if I can give them a 'nudge' or a little troubleshooting guidance to get the pointed in some kind of direction. Additionally, I want to try and educate myself on what the possible root causes might be - curious to know if anyone has had this going on in the past or not.

    If you want more context via the youtube videos of the noise let me know the best way to get those out to you. Thanks in advance for any ideas!

    -Sean

  2. #2
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    When it happens after the system shuts off then that's the refrigerant in the lines equalizing pressures . When it runs the high side is roughly 3x the pressure of the low side. If it bothers you enough to throw a bunch of money at it there are things that can be done to stop it. It's not harming anything now though.

  3. #3
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    Thread Starter
    Thanks for the time taken to reply and the insight! What is strange is that this started happening roughly 3 years ago out of the blue and has been present since then but getting louder and louder over time. It's at the point now where it's driving me nuts, it's loud enough where you can hear it at a loud volume throughout the entire house - after running the loud whine goes on for about 20-40 minutes (since taking the video it's probably double the volume recorded).

    That all said, with your experience and background, I'm curious what things could be done? We've had some airflow issues and there are a couple things we'd probably change if we were to replace any equipment - any info would be good as it might play into some plans we'd already like to pursue.

  4. #4
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    Thread Starter
    PS tried to insert the link to youtube, but no love as I'm under my 7 post limit. If you got to a youtube video, you can edit the url to point at: watch?v=-3r312IMQ2s

  5. #5
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    If you have a heat pump you can go to the thermostat and switch the system from heat to cool for a couple seconds and then switch back to cool. This will energize/de-energize the reversing valve which will quickly equalize the pressures.
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  6. #6
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    Thread Starter
    Thanks for the idea, we have a condenser (Aire Flo AFAIR12B30-A, 12 seer).

  7. #7
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    Quote Originally Posted by seanmcne View Post
    Thanks for the idea, we have a condenser (Aire Flo AFAIR12B30-A, 12 seer).
    That is not a heat pump so there is no reversing valve to shift.
    AOP Rules: Rules For Equipment Owners.

    Free online load calculator: http://www.loadcalc.net/


    There = not here. Their = possessive pronoun. They're = they are
    It's = contraction of it is. Its = the possessive form of it
    Too = also. To = expressing motion. Two = 2
    Then = after that, next. Than = indicates a comparison.
    Questions should end with a question mark "?" Statements end with a period "."

  8. #8
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    Ok, thanks - seems like my next step is probably to call a company, ask for a tech specifically someone to diagnose, and not to take "should be fine" for an answer without a few other options or ideas. I assume this shouldn't suddenly present itself and be getting louder - if anyone does have an idea of a couple things I should ask about or have them dig into (other than the pressure differential) let me know. Thanks!

  9. #9
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    I'd think there's got to be location where this sound is beginning at like a check valve or metering device. Every system equalizes on shutdown but shouldn't make excessive noise. Have a tech open up the service panels and track the sound, this can take some time to locate but is usually repairable in my experience although not necessarily inexpensively. It sounds like your short cycling the compressor by turning the ac on and off real quick which can damage the compressor

  10. #10
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    Had Rheem heat pumps do this. It was the outdoor TXV
    Doug

  11. #11
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    Quote Originally Posted by Makeitcold View Post
    I'd think there's got to be location where this sound is beginning at like a check valve or metering device. Every system equalizes on shutdown but shouldn't make excessive noise. Have a tech open up the service panels and track the sound, this can take some time to locate but is usually repairable in my experience although not necessarily inexpensively. It sounds like your short cycling the compressor by turning the ac on and off real quick which can damage the compressor

    Thanks! I've got a request in for a local place to come out and help diagnose and see if we can get some options laid out - agree on the short cycling, it's only something I've done a few times for troubleshooting/diagnosing and not something we do frequently. If we get it figured out I'll post a response back here to share. Thanks again everyone!

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