Why is my AC making a hissing noise?

July 25, 2019

A hissing noise coming from your HVAC system should not be overlooked. Among the potential 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 could have leaky air ducts. This is annoying, but not necessarily a reason to worry. 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 cease after a few seconds?

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

Is the AC Making a Hissing Sound with Bubbling Noises?

Are you hearing a bubbling sound paired with a hissing sound? This can indicate a refrigerant leak. If a refrigerant leak presents itself, you may hear a light hissing sound as the refrigerant escapes from the leak. Refrigerant escapes as a gas and can be a worrisome health concern. If you have signs of a refrigerant leak, power down the unit and call a professional HVAC company to come evaluate the noise.

If the issue is a valve leak, it should be repaired by a technician as soon as possible. The job of the valves is to regulate the pressurization of the refrigerant gas and if unresolved, the leak will worsen. When it does, the hissing sound will sometimes grow louder, which can be a signal if you’re looking for a cause. You must maintain adequate pressure in your system for it run as intended, and any leak will create additional health and maintenance problems. It’s best to get this fixed post haste if possible.

Are Hissing Noises Coming from the Compressor?

The compressor is found in the exterior air conditioning unit, which is also known as a condenser. Listen quietly for the hissing noise. If you find the compressor is the cause, this could be an unsafe situation because it is an indication that the pressure within the compressor is too great. If you hear hissing, whistling, or shrieking coming from your compressor, power down your air conditioner without delay and call an expert technician.

AC compressor located in exterior condenser unit 

Compressors are some of the most costly parts to repair or replace inside an AC. Compressors are the part responsible for pushing refrigerant through the system. You cannot turn on an air conditioner and cool your home sans compressor. The pricing varies based on factors like 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 provide estimates because of the variable costs, the bill is often high enough to just do a replacement in older air conditioners. This is why it’s crucial to shut off the air conditioning and call a reliable HVAC company if you hear hissing sounds coming from the compressor.

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