Why is my AC making a hissing noise?

July 25, 2019

A hissing noise coming from your HVAC system should not be ignored. Among the possible causes are leaky refrigerant lines, an internal valve leak or a serious problem with your compressor. If the hissing noise is coming from your air ducts, then you may have leaky air ducts. This is annoying, but not necessarily a cause for alarm. A hissing sound could be a sign for any of these things, but we’ll try to narrow it down a little more.

Does the hissing sound end after a few seconds?

If you hear a hissing noise that ceases after a few moments, you may not have any issues. That could be refrigerant in your expansion valve, which is a part of the normal operation of your HVAC mechanicals.

Is the AC Making a Hissing Sound with Bubbling Noises?

Are you hearing a bubbling sound paired with a hissing sound? This may indicate a refrigerant leak. If a refrigerant leak presents itself, you may notice a slight hissing sound as the refrigerant escapes through the leak. It escapes as a gas and can be a worrisome health concern. If you notice signs of a refrigerant leak, shut down the unit and call a expert HVAC company to come inspect the system.

If the cause is a valve leak, it should be repaired by a qualified technician as soon as possible. The job of the valves is to help with the pressurization of the refrigerant gas and if unresolved, the leak will worsen. When it does, the hissing sound will often intensify, which can be a signal if you’re looking for the cause. You must maintain proper pressure in your system for it operate correctly, and any leak will create additional health and maintenance problems. It’s best to get this fixed quickly if possible.

Are Hissing Noises Coming from the Compressor?

The compressor can be found in the exterior air conditioning unit, which is also called a condenser unit. Listen quietly for the hissing noise. If the compressor is the issue, this could be an unsafe situation because it is a sign that the pressure inside the compressor is too much. If you hear hissing, whistling, or shrieking coming from your compressor, power down your air conditioner without delay and call a professional technician.

AC compressor located in exterior condenser unit 

Compressors are some of the most pricey parts to repair or replace inside an air conditioner. Compressors are the part responsible for pushing refrigerant through the system. You cannot run an AC and cool your home sans compressor. The cost varies based on factors such as the type, unit size, and brand requirements. If you have a two stage compressor in the unit today, you will need to replace it with a two stage compressor. It’s impossible to upgrade or downgrade the compressor type - your unit has specific requirements for what components are installed and can’t be MacGyvered. While it’s impossible to give a quote online because of the variable costs, the receipt is frequently high enough to consider a replacement in older units. This is why it’s so important to shut off the air conditioning and call a reputable HVAC company if you hear hissing sounds coming from the compressor.

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