Three Reasons Why Your Air Conditioner Has Started To Whistle While It Works

Posted on: 22 September 2014

Snow White encouraged the Seven Dwarfs to whistle while they worked as a way to bring happiness to their day. However, if your air conditioners have started to whistle while they work, there is certainly nothing happy about the repair bill you could be facing. Some whistling problems can be fixed by you, and identification of the problem is the first step in the repair journey. Here are three causes of air conditioner noise so that you can determine the next step in the repair process.

Foil Tape

Open up the door to the cupboard that houses the indoor portion of your air conditioning unit. You will notice it is made up of two parts. There is the metal box on the bottom that houses the furnace part of the unit. On top of this sits the evaporator coil. The coil is surrounded by foil insulation, and silver foil tape wraps around the bottom of the insulation where it meets the furnace box.

When the foil tape becomes old and worn it loosens, and allows air to move through it. The speed of this air can cause the foil tape to vibrate, and that could be the cause of your whistle.

Foil tape can be purchased by the roll at your local home hardware store. Remove all the existing tape, and replace it with a new strip on each of the four sides of the furnace. Make sure you wipe away all dirt and debris before putting on the new tape so a firm seal can be created.


When was the last time that you replaced the filter on your air conditioning unit? If the whistle began not long after this change, chances are the filter is not properly in place.

Open up the filter door, and give your filter a wiggle to make sure it is sitting exactly where it should be. This small, but important, wiggle may be the fastest whistle cure in history. When the filter is not sitting flush against the floor of the furnace, extra air can move up through the main unit. This extra whoosh of air is another cause of air conditioning whistles, but is the cheapest one to repair as it costs you nothing but time.

Outdoor Fins

If the whistle sound seems to be coming from the outside portion of your system, it is time to head outside to take a look. There are two main reasons why a whistle noise stems from your outdoor condenser. These are:

  1. Each of the four sides of the condenser have fins. When the winds blows, these fins can become clogged up by airborne debris. The more clogged they get, the harder the unit has to work to draw in fresh air. This strain may be the whistle culprit.
  2. Alternatively, the fins on the condenser are easily damaged as they are made of soft metal. If they become bent, or move out of place, their aerodynamic for moving the air is compromised. This also is a possible whistle cause.

Cleaning an outdoor condenser is easy. Simply turn off the power, and clean all four sides with a hose and a scrubbing brush. However, damaged fins need to be repaired by an accredited air conditioner repairer. It is important that they are returned perfectly to their normal state, and this is not a task the average homeowner knows how to do.

If you have not located your whistle after using this checklist, it is time to call in the experts. They can look further inside the unit to see if the coils are clogged, or aerators are blocked. Both of these issues involve removing the cover of the furnace, and that is a step best left to the professionals.

Once the whistle culprit has been identified and removed, you can revert to having an air conditioning unit that does not whistle while it works. But it is working quietly, and that was the main goal all along.