Why is my AC making a loud noise when starting or shutting off?

June 05, 2019

So your AC is functioning well but makes a loud noise when it shuts off. What could be causing it? And could it be a sign that you need repairs to your system?

Causes for AC making a loud noise

  • If you only hear the noise when your unit turns on, the compressor motor is a likely culprit. Another warning of this possibility is if you notice a decrease in the cooling output.
  • Another possibility could be a complication with the dampers. Some air conditioning systems have dampers to change the amount of airflow reaching different parts of your home. The slamming noise may be the damper closing after the AC shuts off.
  • You may also be hearing loud creaking noises from the ducts expanding and contracting from pressure and temperature changes if you have sheet metal ducts.
  • There could also be a problem with the fan or air handler that’s causing the blower wheel to bang against another part of the unit. In some cases, the fan’s mounts can get loose and throw it off balance as it slows down, causing it to hit its enclosure.

As you can see, there are many potential roots of that loud noise you hear when your air conditioner turns on or off. Turn to the Experts for a rapid diagnosis.

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