How To Fix A Window A/C Unit That Is Making A Loud Humming Noise

Posted on: 7 July 2015


If your window air conditioning unit is making a loud humming noise when it is turned on, one of the following problems may be present. Learn how to fix the air conditioner so that it is restored back to its original condition.


  • wire brush
  • wet/dry vacuum cleaner
  • fin tool
  • condenser coil
  • lint-free cloths
  • oil
  • measuring tape
  • weatherstripping
  • scissors

Dirty Condenser Coil With Bent Metal Pieces

Turn off the power to the unit. Remove the front cover. You will see a series of metal pieces that form a grid. This part is referred to as the condenser coil and is responsible for transferring warm air into cool air. Remove dirt from between the metal pieces with a wire brush. Use the hose on a wet/dry vacuum cleaner to assist with collecting the residue.

If the condenser coil's surface is dirty, apply an even coat of coil cleaner to it. Allow the cleaner to penetrate for several minutes and wipe the coil's surface off with a lint-free cloth. Insert one end a fin tool under bent metal pieces and press it firmly to even them out with the adjacent pieces. 

Dirty Fan And Lack Of Oil

The fan that is inside of your unit rests beneath the condenser coil. Try to turn it by hand. If you are having difficulty doing this, dirt may be caught between the blades. Use a damp cloth to wipe them off. Use another cloth to dry the blades. Inspect the motor casing that is connected to the fan and add a few drops of oil to each oil port that is located on it. Place the front cover back on the unit.

Improper Installation And Gaps Around The Unit

Inspect the unit to make sure that it is resting properly in the window. If it looks uneven or if it is tilting, have a friend help you reinstall it. Slide the unit back into place so that it is centered directly underneath the window sash. Balance the unit on top of the windowsill before closing the window. Inspect the sides of the unit. If any gaps are present, cut strips of foam weatherstripping that are the same length as them. Peel off the adhesive backing and press the weatherstripping against the sides of the unit. 

Turn the power back on to the unit. If the humming noise is gone, the problem has been resolved. Keep your unit operating properly by inspecting it throughout the year and cleaning the interior whenever it looks dirty. Inspect the unit to make sure that it hasn't shifted in the window. Replace weatherstripping that has peeled off or that is torn. These steps will prevent your unit from being loud when it is turned on and will help it operate in an efficient manner. Contact a company like Shivani Refrigeration & Air Conditioning for more information.