Why is my AC making a hissing noise?

July 25, 2019

A hissing noise inside your HVAC system should not be disregarded. Among the potential causes are leaking5 refrigerant lines, an internal valve leak or a serious issue with your compressor. If the hissing noise is coming from your ductwork, 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 a little further.

Does the hissing sound end after a few seconds?

If you hear a hissing noise that ceases 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 mechanicals.

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 presents itself, you might hear a slight hissing sound as the refrigerant escapes from the leak. It escapes as a gas and can be a worrisome health concern. If you notice signs of a refrigerant leak, power down the unit and call a qualified HVAC company to come inspect the system.

If the issue is a valve leak, it should be repaired by a qualified technician 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 often intensify, which can be a signal if you’re looking for the cause. You need to maintain adequate pressure in your system for it operate correctly, and any leak will 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 is located in the exterior air conditioning unit, which is also called a condenser. Listen quietly for the hissing noise. If it turns out that the compressor is the cause, this could be an unsafe situation because it is a signal that the pressure within the compressor is too much. If you hear hissing, whistling, or shrieking coming from your compressor, turn off your air conditioner immediately and call an expert technician.

AC compressor located in exterior condenser unit 

Compressors are some of the most pricey units to repair or replace inside an air conditioner. Compressors are the part responsible for cycling refrigerant through the system. You cannot power on an HVAC system and cool your home sans compressor. The pricing is variable based on factors such as the type, unit size, and brand requirements. If you have a two stage compressor in your AC, you would 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 parts are installed and won’t accept substitutes. While it’s impossible to give a quote online because of the variable costs, the bill is often high enough to think about a replacement in older air conditioners. 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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