Why Is My Air Conditioner Making a High Pitch Whistle?

Why Is My Air Conditioner Making a High Pitch Whistle? 11 Feb

An air conditioner is a system designed to cool down a particular space by removing excessive, unnecessary heat. This vital home appliance detects any extreme heat from a specific area. An air conditioner functions similarly to the heated pump but works in a cooling cycle dynamic. It is among the critical components in building and construction since it helps perform a unique task in any room.

Your AC system can break at some point, producing a high-pitched whistle sound that is so irritant to the ears. This happens when the air conditioner system has a low return flow of air. It means that the air conditioner is not getting enough air through vents. Various conditions and factors contribute to air conditioner high pitched whistle. This article lists the five most common causes.

Why is Your AC is Making that High Pitched Whistle?

There are probably plenty of reasons why your air conditioner works bad and gives out those non-friendly noises that piss you off. Here is a summary of the probable causes and what to do in such a scenario.

Cause 1: Dirty Air Filters

The air filters are designed to filter unwanted particles and dust from getting in the air conditioner. If dust is in the air conditioner’s system, proper functioning might have some challenges. When these air filters become dirty, they restrict the airflow, causing overheating. As a result, the air conditioner will make a high pitch sound due to airflow resistance. You can try cleaning the air filters by yourself so it gets enough airflow. This one is probably relatively easy to deal with. However, it can be quite challenging to unclog an air conditioner that has a complex structure. In this case, it is recommended to seek professional assistance. The only solution to this challenge is the replacement of air filters every three months. During summer it’s recommended to replace air filters every month.

Cause 2: Blocked Return Vents

Blocked return vents are the massive vents mostly located in hallways and other open areas. If anything is blocking them, then a proper function of the ducts is not possible. Things such as heavy dust and furniture might create some interference and affect the process in which the air gets in. The supply vents help the AC get airflow into the system, maintaining the airflow. The only solution to this is the removal of any blockages and ensuring all the supply vents are open all the time.

Cause 3: Closed Dampers

These are metal valves located in the ductwork and are used to prevent air delivery to specific parts of the building. The only possible solution for this issue is to put your unit on the inside of the room ensuring proper alignment with the ductwork. This is important to get more airflow to the AC system. In a room where there are too many closed doors, the air supply is affected. If there is minimal airflow in the room, the blower will have to work harder and pull more air. This process of overworking the blower will automatically create the whistling noise experienced from the AC. The possible solution is to ensure that the room is well ventilated to increase airflow.

Cause 4: Copper lines rubbing against each other

Need for alarm? No. When the copper lines outside or inside start rubbing against each other, it produces a loud screeching noise. It could be an issue with the thermostat. When you experience this issue, you will need to change a condenser coil or an air filter. However, this problem would require some keen scrutiny as it could be a little challenging to discover. People often think the issue is more significant than it is, while it could just be some minor problem.

Cause 5: Refrigerant Leaks

If you hear loud rattling whistle noise after switching on the air conditioner – chances are that it’s a refrigerant leak. Refrigerant leaks can be another reason for the air conditioner high pitched whistle. It could be due to increased internal pressure inside your compressor.

This could be very dangerous, so it’s better to call a professional HVAC technician. When this happens, it is highly advisable to switch off the whole AC central power station. If left as it is, it could cause damage. Unfortunately, this problem could only mean one thing that the system has come of age and needs to be replaced. It is because continued use could one day result in major malfunctioning.


Those are some of the common factors that can contribute to the malfunctioning of the air conditioner system. Most of the problems are airflow related problems. With an increasing number of households using ACs, it is essential to be aware of this. The good news is that a little over ninety percent of these issues that cause whistling sounds can be fixed. It is therefore recommended not to panic when you notice such issues. Call an expert to repair your AC system.

Call Smile HVAC

Unfortunately, some of these home appliances and systems do break every once in a while – the air conditioner is not exempted. However, Smile HVAC got you covered. Smile HVAC provides you with the ultimate solution to all your AC problems. We offer quality expert services at affordable rates; you will be surprised! Don’t look further and just know that, at Smile HVAC, we are proud of providing the best quality and affordable services to clients all over the Great Toronto Area. So, the next time you have a problem with your AC, give us a call and we will handle it for you in no time!