Why is my AC making a hissing noise?

July 25, 2019

A hissing noise coming from your HVAC system should not be disregarded. Among the potential causes are leaky refrigerant lines, an internal valve leak or a serious failure with your compressor. If the hissing noise is originating from your ductwork, then you could have leaking air ducts. This is annoying, but not necessarily a reason to worry. A hissing sound may indicate 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 stops after a few seconds, you may not have any issues. That could be refrigerant in your expansion valve, which is part of the normal 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 can indicate a refrigerant leak. If a refrigerant leak is present, you may notice a light hissing sound as the refrigerant escapes through the leak. The coolant escapes as a gas and can be a serious health concern. If you have signs of a refrigerant leak, power down your HVAC and call a qualified HVAC company to come inspect the system.

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 help with the pressurization of the refrigerant gas and if unresolved, the leak will worsen. When it does, the hissing sound will sometimes grow louder, which can be a signal if you’re looking for the cause. You need to maintain proper pressure in your system for it cool your home, and refrigerant leaks cause additional health and maintenance problems. You want to get this fixed post haste if possible.

Are Hissing Noises Coming from the Compressor?

The compressor can be found in the outdoor air conditioning unit, which is also called a condenser. Listen around here for the hissing noise. If it turns out that the compressor is the cause, this could be a hazardous situation because it is a sign that the pressure inside the compressor is too much. If you hear hissing, whistling, or shrieking coming from your compressor, shut off your air conditioner pronto 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. Compressors are the part responsible for pushing refrigerant through the system. You cannot turn on an air conditioner and cool your home without a compressor. The pricing is variable based on factors like the type, unit size, and brand requirements. If you have a two stage compressor in the unit today, 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 components are installed in order to operate safely. While it’s impossible to say how much a compressor replacement is because of the variable costs, the expense is often large enough to just do a replacement in older units. This is why it’s crucial 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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