Why is my AC making a hissing noise?

July 25, 2019

A hissing noise coming from your HVAC system is not something to be overlooked. Among the potential causes are leaky refrigerant lines, an internal valve leak or a serious issue with your compressor. If the hissing noise is originating from your ducts, then you may have leaky air ducts. This is annoying, but not necessarily something to panic over. A hissing sound may be a sign for any of these things, but we’ll try to narrow it down a little more.

Does the hissing sound end after a few seconds?

If you hear a hissing noise that stops after a few seconds, you may not have any problems. That could be refrigerant in your expansion valve, which is part of the normal 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 could indicate a refrigerant leak. If a refrigerant leak is present, you might notice 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 see signs of a refrigerant leak, turn off the AC and call a qualified HVAC company to come take a look.

If the issue 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 without repair, the leak will worsen. When it does, the hissing sound will often intensify, which can be a signal if you’re looking for a cause. You must maintain proper pressure in your system for it run as intended, and any leak will 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 can be located in the outdoor air conditioning unit, which is also called a condenser. Listen nearby the condenser for the hissing noise. If it turns out that the compressor is the issue, this could be a dangerous 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 immediately and call a professional technician.

AC compressor located in exterior condenser unit 

Compressors are some of the most pricey units to repair or replace inside an AC unit. 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 expense varies 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 parts are installed and can’t be MacGyvered. While it’s impossible to provide estimates because of the variable costs, the bill is frequently large enough to just do a replacement in older units. This is why it’s so important 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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