Why is my AC making a hissing noise?

July 25, 2019

A hissing noise inside your HVAC system is not something to be disregarded. Among the potential causes are leaking5 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 cause for alarm. A hissing sound may be a sign for any of these things, but we’ll try to narrow it down a little further.

Does the hissing sound cease after a few seconds?

If you hear a hissing noise that ends after a few seconds, 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 mechanicals.

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 may notice a light hissing sound as the refrigerant escapes via 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 professional HVAC company to come take a look.

If the issue is a valve leak, it should be repaired by a qualified technician as soon as possible. The job of the valves is to manage the pressurization of the refrigerant gas and without repair, the leak will worsen. When it does, the hissing sound will increase, which can be a tell if you’re looking for a cause. You need to maintain proper pressure in your system for it run as intended, and leaks create additional health and mechanical problems. You ought to get this fixed post haste if possible.

Are Hissing Noises Coming from the Compressor?

The compressor is located in the exterior air conditioning unit, which is also called a condenser. Listen quietly for the hissing noise. If the compressor is the issue, this could be a dangerous situation because it is an indication that the pressure in the compressor is too much. If you hear hissing, whistling, or shrieking coming from your compressor, turn off your air conditioner immediately and call a professional technician.

AC compressor located in exterior condenser unit 

Compressors are some of the most costly units to repair or replace inside an AC unit. Compressors are the part responsible for circulating refrigerant through the system. You cannot run an AC and cool your home without a compressor. The expense changes based on factors such as the type, unit size, and brand requirements. If you have a two stage compressor in your AC, you would 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 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 bill is often high enough to just do a replacement in older ACs. 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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