Why is my AC making a hissing noise?

July 25, 2019

A hissing noise coming from your HVAC system is not something to be disregarded. 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 ductwork, then you might have leaking air ducts. This is annoying, but not necessarily a cause for alarm. A hissing sound could indicate any of these things, but we’ll try to narrow it down further.

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 problems. That could be refrigerant in your expansion valve, which is 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 along with a hissing sound? This may indicate a refrigerant leak. If a refrigerant leak presents itself, you might hear 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, turn off your HVAC and call a professional HVAC company to come take a look.

If the problem is a valve leak, it should be repaired by a professional as soon as possible. The job of the valves is to help with the pressurization of the refrigerant gas and left alone, the leak will worsen. When it does, the hissing sound will sometimes grow louder, which can be a sign if you’re looking for a cause. You need to 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 quickly if possible.

Are Hissing Noises Coming from the Compressor?

The compressor is found in the outdoor air conditioning unit, which is also called a condenser. Listen quietly for the hissing noise. If it turns out that the compressor is the issue, this could be an unsafe situation because it is a signal that the pressure within the compressor is too high. If you hear hissing, whistling, or shrieking coming from your compressor, shut off your air conditioner immediately and call an HVAC technician.

AC compressor located in exterior condenser unit 

Compressors are some of the most costly units to repair or replace inside an air conditioner. 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 cost varies based on factors like the type, unit size, and brand requirements. If you have a two stage compressor in your AC, 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 parts are installed in order to operate safely. While it’s impossible to give a quote online because of the variable costs, the expense is often high enough to consider a replacement in older units. 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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