Why is my AC making a hissing noise?

July 25, 2019

A hissing noise coming from your HVAC system should not be overlooked. 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 ductwork, then you may 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 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 a 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 paired with a hissing sound? This can 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 serious health concern. If you see signs of a refrigerant leak, power down the AC and call a professional HVAC company to come evaluate the noise.

If the cause is a valve leak, it should be repaired by a professional as soon as possible. The job of the valves is to regulate the pressurization of the refrigerant gas and if unresolved, the leak will worsen. When it does, the hissing sound will increase, which can be a signal if you’re looking for the cause. You need to maintain proper pressure in your system for it run as intended, and any leak will create additional health and maintenance problems. You want to get this fixed quickly if possible.

Are Hissing Noises Coming from the Compressor?

The compressor is located in the exterior air conditioning unit, which is also known as a condenser unit. Listen nearby the condenser 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 inside the compressor is too high. If you hear hissing, whistling, or shrieking coming from your compressor, shut off your air conditioner pronto and call an HVAC 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 turn on an air conditioner 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 now, 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 and can’t be MacGyvered. While it’s impossible to give a quote online because of the variable costs, the expense is frequently large enough to consider a replacement in older ACs. This is why it’s so important to shut off the air conditioning and call a trustworthy HVAC company if you hear hissing sounds coming from the compressor.

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