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A/C banging on compressor shutoff

Weak springs. If the 20 yo unit has never had a condenser coil cleaning, it wouldn't hurt. It just depends on whether she wants to service the exisiting one and live with the noise or get a new one.


  • Mike M.Mike M. Member Posts: 22

    My 85 year old mother is having a problem with the through-wall air conditioner in her apartment. It is presumably 20+ years old and cools fine but about 2 out of 3 times when the compressor cycles off it does so with VERY loud banging and rattling. And then once in awhile it will do some further rattling about 5 seconds after that. The building mangager doesn't seem to want to do anything about it.

    What might the cause be and would it be worthwile for her to hire someone on her own to look at it or is it beyond repair.
  • EmpireEmpire Member Posts: 2,343
    Hello Mike M.

    At 20 years old, it could be a lot of things. Moving parts ware and this could be from the compressor or the double shaft fan motor coming to a stop. It's hard to tell. It's like the Midas commercial where you describe the sound or mimic it and we try to guess what's wrong...:-) Seeing that you compressor is reciprocating style, could be worn valves, loose mounting bolts etc...

    Mike T.
  • WayneWayne Member Posts: 2
    broken or weak springs

    Broken or weak springs inside the compressor shell. The springs take the torque of the motor when starting/stopping. As the unit ages, the springs become weak or break, allowing the pump/motor to hit the compressor shell making the noise.

    The condenser coil is probably dirty, creating a higher discharge pressure, more torque on the motor, the torque unwinds when the power is removed.

    At 20 years of age, the unit may not justify more then a condenser coil cleaning at best.

  • Eugene SilbersteinEugene Silberstein Member Posts: 1,380
    Definitely sounds like an internal mounting problem

    As mentioned, it sounds like there is a problem with the internal motor mounts in the compressor.

    Normally, when the unit is relatively new, the mounts can handle the vibrations both on startup and shut down with no problem.

    I'm not certain that a coil cleaning will help much since, even if the coil is dirty, both the high side and low side pressures will rise. The pressure differential across the compressor will, for the most part, remain relatively close.

    Also, if the coil was indeed dirty, your mother would likely be complaining that the unit is not cooling well.

This discussion has been closed.


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