You don’t want to ignore the hissing sound coming from your air conditioning unit. It could be a sign of a significant issue, such as an internal valve leak, or a less severe problem, such as a leaky air duct. Consider the following factors when dealing with a hissing sound from your air conditioner.

Thermostatic Expansion Valve

As your air conditioning system converts liquid refrigerant to vapor in the evaporator coil, the expansion valve plays a vital role in regulating the pressure drop. This allows the refrigerant to expand into a gaseous state, and the expansion valve maintains a consistent flow of refrigerant by managing the evaporator pressure. As it goes through this process, the expansion valve may make a brief hissing noise as part of the normal operation of the HVAC unit. If you hear this noise intermittently, there’s no need to worry. However, if you hear this noise constantly or notice that the noise fluctuates in pitch and becomes a screeching or whistling sound, you should have our HVAC technicians review your air conditioner.

Refrigerant Leak

If you hear a hissing sound from your air conditioner, one of the primary and most problematic causes could be a refrigerant leak. When your AC unit lacks coolant, it cannot cool your home and may even end up heating it. If warm air is blowing through your vents with a hissing noise and a bubbling sound, it is a good indication that you could have a refrigerant leak.

If the valve in your AC unit is the source of the leak and remains unresolved, the leak will only worsen. The hissing sound may then become more persistent. Leaking refrigerant can be harmful to your health, so it is crucial to address a refrigerant leak promptly.

High Pressure in the Air Compressor

When the refrigerant traveling through your air conditioner doesn’t cool enough, it can cause high pressure in the compressor that results in a hissing sound. Although it is not a common problem, it can occur due to incorrect installation, an aging system, or extremely hot and humid weather. If you determine that the hissing noise is due to excessive pressure in the air compressor, it is essential to turn off your unit immediately and seek assistance from a technician to get it serviced.

Heat Pump Reversing Valve

If the reversing valve in your heat pump malfunctions or becomes stuck between the heating and cooling modes, you may notice a hissing sound. The reversing valve is responsible for reversing the flow of refrigerant in your heat pump, allowing it to heat and cool your home.

Copper Tubing Damage or Poor Installation

Debris, falling branches, or lawn care equipment can cause physical damage to your air conditioner. This damage can cause copper pipes that connect to the outdoor coils on top of the HVAC system to experience leaks that produce a hissing noise. During air conditioner installation, technicians use a method called “brazing” to create an airtight connection between the line set and the air conditioner. If the brazing is not done correctly, a leak can develop that may cause a hissing noise. Although a leak from improper brazing may not immediately present itself, it can form over time and worsen rapidly. Any issues arising from copper pipe damage or poor brazing during installation will require the help of an experienced service technician.

Leaking Ductwork

As time passes, cracks, gaps, or tears can develop in your air conditioning ductwork, allowing air to escape. When this occurs, you may hear a high-pitched whistling or hissing sound emanating from the vents, which is caused by pressurized air leaving the air ducts. Signs that leaky ductwork may be responsible for the hissing include difficulty maintaining a cool temperature in your home because the conditioned air is escaping into your basement, ceiling, attic, and crawl spaces. Additionally, you may notice an increase in energy bills as your air conditioner works harder to compensate for the air escaping into your ducts.

High-Quality Heating and Cooling in Mishawaka

At Tyler’s Heating & Cooling, we have been providing high-quality HVAC service to our customers since 2017. We are a veteran-owned team that takes pride in giving our customers professional, on-time service every single time. We are happy to provide service in both residential and commercial settings, and we bring our family values to each job we do.

Our services include HVAC repair, installation, and maintenance. Our plumbing services include general repair, new plumbing installation, drain cleaning, water heater repair, and cistern maintenance. Contact Tyler’s Heating & Cooling today to learn more about our professional HVAC and plumbing services.

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