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 possible causes are leaky refrigerant lines, an internal valve leak or a serious issue with your compressor. If the hissing noise is originating from your ductwork, then you may have leaking air ducts. This is annoying, but not necessarily something to panic over. A hissing sound may indicate any of these things, but we’ll try to narrow it down further.

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 issues. That can be refrigerant in your expansion valve, which is part of the normal day to day 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 presents itself, you might hear a slight hissing sound as the refrigerant escapes via the leak. The coolant escapes as a gas and can be a major health concern. If you have signs of a refrigerant leak, shut down the unit and call a professional 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 often intensify, which can be a tell if you’re looking for a cause. You must maintain proper pressure in your HVAC system for it operate correctly, and leaks 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 exterior air conditioning unit, which is also known as a condenser. Listen around here for the hissing noise. If it turns out that the compressor is the problem, this could be an unsafe situation because it is a sign that the pressure within the compressor is too high. 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 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 without a compressor. The expense is variable based on factors like 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 compressors are installed and won’t accept substitutes. While it’s impossible to say how much a compressor replacement is because of the variable costs, the expense is often high enough to consider a replacement in older units. This is why it’s crucial 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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