Why is my AC making a hissing noise?

July 25, 2019

A hissing noise inside your HVAC system should not be overlooked. Among the probable causes are leaking5 refrigerant lines, an internal valve leak or a serious issue with your compressor. If the hissing noise is coming from your air ducts, then you might have leaky 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 further.

Does the hissing sound end after a few seconds?

If you hear a hissing noise that ceases after a few seconds, you may not have any issues. That can be refrigerant in your expansion valve, which is part of the normal day to day 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 could indicate a refrigerant leak. If a refrigerant leak is present, you might notice a light 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 AC and call a qualified HVAC company to come evaluate the noise.

If the problem 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 tell if you’re looking for the cause. You must maintain adequate pressure in your system for it operate correctly, and leaks create additional health and mechanical problems. It’s best 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 nearby the condenser for the hissing noise. If the compressor is the issue, this could be a dangerous situation because it is a signal 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 a professional technician.

AC compressor located in exterior condenser unit 

Compressors are some of the most costly parts to repair or replace inside an air conditioner. Compressors are the part responsible for pushing refrigerant through the system. You cannot power on an HVAC system and cool your home sans compressor. The cost changes 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 won’t accept substitutes. While it’s impossible to say how much a compressor replacement is because of the variable costs, the receipt is frequently big enough to just do a replacement in older ACs. This is why it’s critical 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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