Why is my AC making a hissing noise?

July 25, 2019

A hissing noise coming from your HVAC system is not something to be ignored. Among the probable causes are leaky refrigerant lines, an internal valve leak or a serious issue with your compressor. If the hissing noise is coming from your ducts, then you might have leaking air ducts. This is annoying, but not necessarily a reason to worry. A hissing sound may indicate 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 can be refrigerant in your expansion valve, which is a part of the normal day to day operation of your HVAC system.

Is the AC Making a Hissing Sound with Bubbling Noises?

Are you hearing a bubbling sound along with a hissing sound? This can indicate a refrigerant leak. If a refrigerant leak develops, you might notice a slight hissing sound as the refrigerant escapes via the leak. It escapes as a gas and can be a serious health concern. If you see signs of a refrigerant leak, power down the unit and call a qualified HVAC company to come take a look.

If the problem 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 tell if you’re looking for the cause. You need to maintain adequate pressure in your HVAC system for it cool your home, and leaks create additional health and maintenance problems. You want to get this fixed quickly if possible.

Are Hissing Noises Coming from the Compressor?

The compressor is located in the exterior air conditioning unit, which is also known as a condenser. Listen quietly for the hissing noise. If the compressor is the issue, this could be a hazardous situation because it is a signal that the pressure within the compressor is too much. If you hear hissing, whistling, or shrieking coming from your compressor, turn off your air conditioner without delay and call an expert technician.

AC compressor located in exterior condenser unit 

Compressors are some of the most pricey parts to repair or replace inside an AC unit. Compressors are the part responsible for pushing refrigerant through the system. You cannot run an AC and cool your home sans compressor. The expense changes 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 another two stage compressor. It’s not possible to upgrade or downgrade the compressor type - your unit has specific requirements for what parts are installed and can’t be MacGyvered. While it’s impossible to provide estimates because of the variable costs, the expense is often high enough to just do a replacement in older units. This is why it’s crucial to shut off the air conditioning and call a trustworthy HVAC company if you hear hissing sounds coming from the compressor.

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