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I am calling a HVAC technician since this is probably too complex a problem for me, but wanted to hear some possible diagnosis.

The symptoms are as follows:

  • The A/C is working well during the day (or so it seems).
  • For the past three nights however I wake up and it feels hot.
  • The thermostat reads 75°F and it is set at 72°F.
  • Most importantly a loud vibrating noise is coming from the basement and it is the HVAC unit. This has never happened during the day.
  • I shut off the AC and turn on the fan only and I still get the loud noise and vibration.
  • After an hour or so, I can hear liquid dripping inside the unit.

Anyone knows what might be the problem? What other information could be useful?

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1 Answer 1

up vote 1 down vote accepted

It sounds like your coils are freezing over. This could simply been the result of not changing your filter, or the coils need cleaning, so there isn't enough warm airflow over the coils. It's also possible that you're running the unit when it's too cold outside. If it gets below 60°F you should be opening your windows instead of running the AC.

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I should mention that when the vibrating noise happens poor to no airflow is felt at the vents. When coils freeze, do they prevent proper airflow? –  sturgman Sep 1 '13 at 19:23
Yes, it will block airflow. Air cannot pass through ice. –  BMitch Sep 1 '13 at 19:24

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