Why is my AC making a hissing noise?

July 25, 2019

A hissing noise inside your HVAC system is not something to be ignored. Among the possible causes are leaking5 refrigerant lines, an internal valve leak or a serious failure with your compressor. If the hissing noise is originating from your air ducts, then you might have leaky 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 a little more.

Does the hissing sound cease after a few seconds?

If you hear a hissing noise that ends after a few moments, you may not have any problems. That might 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 may indicate a refrigerant leak. If a refrigerant leak presents itself, you might hear a slight hissing sound as the refrigerant escapes from the leak. The coolant escapes as a gas and can be a major health concern. If you see signs of a refrigerant leak, turn off the AC and call a expert HVAC company to come evaluate the noise.

If the cause 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 if unresolved, the leak will worsen. When it does, the hissing sound will often intensify, which can be a sign if you’re looking for a cause. You must maintain adequate pressure in your HVAC system for it run as intended, and any leak will create additional health and mechanical problems. You want to get this fixed post haste 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 unit. Listen around here for the hissing noise. If it turns out that the compressor is the problem, this could be an unsafe situation because it is a signal that the pressure in the compressor is too great. If you hear hissing, whistling, or shrieking coming from your compressor, shut off your air conditioner without delay and call a professional technician.

AC compressor located in exterior condenser unit 

Compressors are some of the most expensive units 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 without a compressor. The cost 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 another two stage compressor. It’s impossible to upgrade or downgrade the compressor type - your unit has specific requirements for what compressors 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 just do a replacement in older units. This is why it’s critical 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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