The noise from an air conditioning unit can have lots of causes depending on the type of unit. These noises should not be ignored and are almost always a sign something that has gone wrong or is in the process of going wrong. The type of noise may be used to diagnose the nature of the problem. Ignoring it allows the problem to worsen to the point where it cannot be fixed, or where fixing it will be very expensive. In some cases, an air conditioning unit is beyond repair by the time it starts being noisy; however, much of the time the unit will need only minor work done in order to start functioning quietly again. In this post I will focus on some of the more common noise sources in a window unit.


Fixes for Noisy Fans

For a fan to work properly, it will need to be kept clean and to be properly maintained. The first step is to locate the source of the noise. Fans that produce a rattling or harsh humming noise may be loose or need cleaning.

  • Open the air conditioner cabinet and locate the fan. Remove any debris you see on or around the blades. In some cases insulation or other items may fall into the unit and be noisy due to the movement of the blades.
  • If the problem is not debris, then check to see if the blade itself is loose. If so, then you can tighten the screw at the hub with a screwdriver or Allen wrench.
  • Check to make sure that the blades are straight. A blade with even a slight bend may be touching the inside of the unit which will produce a noise. The blades may be bent back into place, but you will have to be gentle and precise in handling them.



A motor that needs lubrication may emit a humming or grinding noise. Some units come with unsealed motors and you will be able to apply lubrication in the form of SAE 10 oil placed in the oil ports. You may prevent the occurrence of noise by oiling the air conditioner motor at the beginning of each summer.


Loose Screws

When an air conditioner unit is working, it vibrates; this vibration can cause screws in the unit to come loose. Many of the problems that make air conditioning units noisy are the result of screws in panels throughout the unit that have been vibrated loose. The mounting screws that are holding the unit in place can also be loosened as the unit operates. Both situations will produce a rattling noise when the air conditioner is putting out air. These can all be easily fixed with a few turns of your screwdriver.


Coil Fins

If the coil fins have become clogged with dirt, the air conditioning unit may become noisy. Check to see if this is so; if it needs cleaning use a vacuum cleaner with a brush attachment to remove any dirt or debris. Bent coil fins can also cause the unit to emit a humming noise; these may be straightened with the use of a tool made for this purpose: the fin comb. Insert the teeth of the fin comb between the coil fins and slide to straighten the bent fins.

These simple steps can save time and money and are relatively simple for a homeowner to do. However, if the problem persists, an HVAC contractor should be contacted.