Why is my AC making a hissing noise?

July 25, 2019

A hissing noise inside your HVAC system should not be disregarded. Among the possible causes are leaking5 refrigerant lines, an internal valve leak or a serious failure with your compressor. If the hissing noise is heard from your ducts, then you could have leaky air ducts. This is annoying, but not necessarily a reason to worry. A hissing sound could be a sign for 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 issues. That can 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 paired with a hissing sound? This can indicate a refrigerant leak. If a refrigerant leak presents itself, you might notice a light hissing sound as the refrigerant escapes from the leak. The coolant escapes as a gas and can be a worrisome health concern. If you notice signs of a refrigerant leak, shut down the AC and call a professional HVAC company to come inspect the system.

If the problem is a valve leak, it should be repaired by a technician 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 sometimes grow louder, which can be a signal if you’re looking for a cause. You need to maintain adequate pressure in your system for it run as intended, and leaks create additional health and maintenance problems. You want to get this fixed quickly if possible.

Are Hissing Noises Coming from the Compressor?

The compressor can be found in the outdoor air conditioning unit, which is also known as a condenser. Listen around here for the hissing noise. If you find the compressor is the cause, this could be a dangerous situation because it is a signal that the pressure inside the compressor is too much. If you hear hissing, whistling, or shrieking coming from your compressor, power down your air conditioner pronto and call an expert 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 cycling refrigerant through the system. You cannot run an AC and cool your home without a compressor. The expense changes based on factors such as the type, unit size, and brand requirements. If you have a two stage compressor now, you would 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 bill is often big enough to just do a replacement in older air conditioners. This is why it’s critical 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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