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  1. #1
    Join Date
    Jun 2008
    Posts
    12

    Lennox a/c unit makes loud noise on startup

    Hi there,

    We have two Lennox 13Acd outside units. One upstairs and a smaller one downstairs 13ACD-030-230-03. The smaller one at times makes a nasty noise at startup. I've recorded the noise

    http://www.youtube.com/watch?v=rzH_66MDYng


    You can hear the upstairs one running during the first part of the video and then the downstairs unit kicks on with a nasty racket.

    I've had the folks that installed the units take a look. They thought it was the fan motor and replaced the motor. This didn't make a difference. They are still convinced this is somehow the fan motor making the noise.

    I've seen references to possible freon pooling where the noise occurs when all the freon has to be pumped back up. The noise occurs more frequently when it's hot outside. Both units have the inside unit up in the attic.

    What is that awful noise?

    Thanks,
    Brian

  2. #2
    Join Date
    Jan 2007
    Location
    NE OHIO
    Posts
    778
    my guess is that its way overcharged

  3. #3
    Join Date
    Jun 2008
    Posts
    12
    They did check the charge and said it was fine.

  4. #4
    Join Date
    Jan 2007
    Location
    NE OHIO
    Posts
    778
    and did they say why it sounded horrible?

  5. #5
    Join Date
    Nov 2001
    Location
    east kansas
    Posts
    8,032
    Hard to tell from here with all the background noise of the other unit running. I Believe I would have shut the other off before making the video.
    Beware of advice given by some guy on the Internet.

  6. #6
    Join Date
    Mar 2007
    Location
    Myrtle Beach, SC
    Posts
    2,919
    There is a sound blanket available for that compressor. But it sounds over charged to me.
    Remember, Air Conditioning begins with AIR.

  7. #7
    Join Date
    Jun 2008
    Posts
    12
    Young_tech: They believe it's an issue still with the fan motor as the tech said when the noise was made the fan delayed for a second before starting.

    Milk_man: I agree it would be better if the other unit wasn't running, unfortunately it kicked on before my wife could kick on the downstairs unit. I will attempt one without the upstairs unit running. Thanks for taking a look.

  8. #8
    Join Date
    Mar 2007
    Location
    Myrtle Beach, SC
    Posts
    2,919
    Quote Originally Posted by brboot View Post
    They did check the charge and said it was fine.
    Did they check sub-cooling or just the pressures?
    Remember, Air Conditioning begins with AIR.

  9. #9
    Join Date
    Mar 2009
    Location
    Brevard County, FL
    Posts
    582
    Quote Originally Posted by brboot View Post
    Young_tech: They believe it's an issue still with the fan motor as the tech said when the noise was made the fan delayed for a second before starting.
    You said that they replaced the fan motor already and it is still making the same noise? Doesn't make a lot of sense to me. From afar I tend to agree with the overcharge guess.

    What else have they done to diagnose the system besides saying that the charge was fine?

    My advice would be to request a different tech or even a different contractor since they already changed the motor and are still convinced that it is the motor causing the noise.
    "If you aren't living on the edge, you are taking up to much space!"

  10. #10
    Join Date
    May 2000
    Location
    Indianapolis, IN, USA
    Posts
    34,084
    On an attic coil, it's best to loop the suction line UP as it comes out of the coil past the top of the coil then go down outside. That can stop liquid in the coil from flowing by gravity down to the compressor during the off cycle. If neither are this way, that might not be what's happening. Hard to say. Certainly ain't a happy compressor when it starts. Looping up doesn't stop it, maybe strapping a crankcase heater on would help. Covering may lower the sound but doesn't help the damage the slugging can cause.

  11. #11
    Join Date
    Jun 2008
    Posts
    12
    Quote Originally Posted by kevster View Post
    You said that they replaced the fan motor already and it is still making the same noise? Doesn't make a lot of sense to me. From afar I tend to agree with the overcharge guess.

    What else have they done to diagnose the system besides saying that the charge was fine?

    My advice would be to request a different tech or even a different contractor since they already changed the motor and are still convinced that it is the motor causing the noise.

    It doesn't make sense to me either. I'm not sure how they checked the charge(sub-cooling or just pressure).

    Other items they have checked are capacitors and voltages. All check out. What other items should be checked besides sub-cooling?

  12. #12
    Join Date
    Apr 2010
    Location
    Minnesota
    Posts
    517
    Pretty hard to tell from here if it's overcharged or not. If you had a qualified tech say that it's charged correctly, why would they zero in on the fan motor? Hmmm... Maybe because that's where the noise is coming from? It's not hard to run just the compressor for a few seconds, or the fan only for a few seconds.

    I had this same scenario a few years back, and I replaced the fan motor, didn't do any good. It ended up being the fan blade making the noise. The hub wasn't properly pressed onto the prop, making a terrible vibration. May be something to look into. Good luck.

  13. #13
    Join Date
    Apr 2010
    Location
    Minnesota
    Posts
    517
    If it is truly the compressor making the noise, start with putting on a crankcase heater. Might need a LL solenoid too.

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