Why is my AC making a hissing noise?

July 25, 2019

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

Does the hissing sound stop 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 unit.

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 develops, you might hear a light hissing sound as the refrigerant escapes via the leak. The coolant escapes as a gas and can be a serious health concern. If you notice signs of a refrigerant leak, power down the AC and call a professional HVAC company to come inspect the system.

If the issue is a valve leak, it should be repaired by a professional as soon as possible. The job of the valves is to manage the pressurization of the refrigerant gas and left alone, 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 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 can be located in the exterior air conditioning unit, which is also called a condenser unit. Listen nearby the condenser for the hissing noise. If it turns out that the compressor is the cause, this could be an unsafe situation because it is an indication that the pressure in the compressor is too great. If you hear hissing, whistling, or shrieking coming from your compressor, switch 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 cycling refrigerant through the system. You cannot run an AC and cool your home sans compressor. The expense is variable 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 not possible 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 bill is often large enough to think about a replacement in older units. 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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