An air conditioner is essential for keeping your indoor environment livable and cool. Because your AC is a piece of equipment with various moving components, it is natural for this appliance to make a few sounds during operation. For example, you might have heard the sound of an AC cycle stopping or restarting. The occurrence of loud and bothersome noises such as hissing or clanging can indicate serious problems. A look at the top causes of hissing noise can help you understand what to do in this scenario and when it is time to contact an HVAC professional for help.

What Causes Hissing Sounds?

When the weather gets warmer, it is your air conditioner’s job to keep the indoor temperature comfortable. Unfortunately, there are few air conditioner problems more frustrating than incessant hissing sounds. Causes of hissing noises can include refrigerant leaks, compressor problems, duct leaks, or internal mechanical problems.

Refrigerant Leaks

Refrigerant leaks are among the most common causes of hissing noises from your air conditioner. Refrigerant is a fluid essential to each cooling cycle. This fluid undergoes a cyclical phase transition from liquid to gas and back again in order to cool your room. But when refrigerant leaks, the fluid quickly escapes the machine in gas form and creates a distinctive hissing or bubbling noise. Other signs of a refrigerant leak include frost or ice on the AC, vents blowing warm or hot air, water leaking from the outdoor unit, or a higher utility bill. If you suspect a refrigerant leak, it is important to contact an HVAC professional right away. Since refrigerant spills can contaminate your immediate environment, you should not attempt to change or refill this fluid yourself.

High Pressure in the Compressor

Extreme pressurization within the compressor can also cause a hissing noise. The compressor is an AC component that helps move pressurized refrigerant through the system. But when the pressure within a compressor builds too high, it can make a high-pitching hissing sound. Most homeowners notice the loud hissing or screeching soon after turning the AC on, and the sound tends to last at least 10 to 15 seconds. If there is too much pressure within the system, you may also notice that the AC cycle starts and stops more often than normal.

In addition, some modern AC units have sensors that monitor internal pressure and shut down the appliance if the pressure builds too high. This means that the unit will not turn back on until pressure dissipates. This occurrence often requires intervention from a professional. An HVAC service technician can locate the source of the compressor problem and make repairs as needed.

Leaking Air Ducts

Leaky air ducts can also cause a hissing noise. As your air conditioner ages, the AC ducts can deteriorate and develop small holes or cracks. Hissing sounds occur when the air escapes through these gaps. You may also hear a high-pitched whistling noise from the vents as a result of the air forcing its way through holes in your AC ducts. In addition to the persistent hissing sound, you may also find it harder to keep your home cool since the conditioned air escapes. This lost air may end up in places like your walls, ceilings, or crawl spaces. In addition, you may notice an increase in utility bills as your unit works harder to maintain temperatures and compensate for lost air that escapes from the ducts. An HVAC professional can conduct a thorough inspection or energy audit and repair leaking ductwork.

Damage From Debris

Air conditioners can also make hissing noises after damage from foreign objects or debris. This damage typically occurs on the outside portion of your AC unit. Things like fallen leaves or branches can clog or disrupt the function of a unit. Even physical impact from power tools or lawn mowers can compromise the functionality of your AC. Fortunately, an HVAC professional can inspect your AC unit and provide repairs or reinforcements as needed.

Air Filter Issues

Air filters trap unwanted particulates and help prevent contaminants from entering your AC system. If air filters become too clogged or dirty, however, these devices become ineffective. Inadequate air filters can also be the reason for a hissing sound, as your AC works hard to perform despite the presence of clogs and impurities.

Dysfunctional Motor

Faulty motors can make several types of unusual sounds. For many AC models, the motor makes a hissing noise if it overheats or if there are problems with the internal wiring. In either scenario, it is best to allow a professional to inspect the motor so that it does not blow out. If the motor experiences a catastrophic breakdown, you could end up needing to purchase a new unit.

Thermostatic Expansion Valve Operation

It’s important to note that your AC unit can make hissing noises that are entirely normal. These hissing sounds typically come from the thermostatic expansion valve. The purpose of this valve is to control the amount of refrigerant released to the AC evaporator section and to monitor refrigerant pressure. This expansion valve can make slight hissing sounds during operation, and you will typically hear these soft sounds indoors. If you hear persistent hissing that changes in volume or pitch, it is time to reach out to experts for help.

What Can I Do If I Hear Hissing Sounds?

If you hear a hissing noise coming from your air conditioner, it is imperative to contact an HVAC company to inspect, diagnose, and repair the problem. Before calling the company, you may wish to note the volume of the noise and how frequently it occurs. You may also make a note of whether the hissing is more audible indoors or outdoors. This will allow an HVAC technician to identify the root cause of the issue. Common solutions for hissing problems include checking for refrigerant leaks or problems with the air ducts or filters. If you inform your technician that the hissing sounds also include bubbling noises, the technician can check the likely source of refrigerant leakage.

How Do I Prevent the Occurrence of Hissing Sounds?

Some hissing sounds occur as your unit wears out over time or if it works extra hard during a heat wave. While you cannot prevent these occurrences, there are steps you can take to reduce the likelihood of hissing sounds. For example, keep up with your AC maintenance by changing the filters regularly. An HVAC professional can help you choose an air filter with an appropriate MERV rating so that it performs as efficiently as possible. In addition, it is also important to keep up with seasonal AC maintenance. During maintenance sessions, a technician can check refrigerant levels, test the air pressure, monitor the compressor, and ensure that your unit is clean and free of debris. You may also wish to sign up for a maintenance plan so that you never miss a seasonal appointment. Regular maintenance can also help preserve the longevity of your unit.

Contact Us Today

Hissing noises coming from your AC can sound alarming. Fortunately, HVAC professionals are here to help. Precision Heating & Air provides air conditioner services to homes in Dallas, GA, as well as Metro Atlanta and the surrounding areas. We offer AC installation and replacement as well as air conditioner repair. If the hissing noises escalate into serious problems, we also provide emergency HVAC services. Our technicians are experts in indoor air quality and related services like dehumidifiers and air purification devices. We offer MVP memberships as well as rebates and a referral program. Contact Precision Heating & Air for all of your AC needs.

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