Why is my AC making a hissing noise?

July 25, 2019

A hissing noise coming from your HVAC system is not something to be ignored. Among the probable causes are leaky refrigerant lines, an internal valve leak or a serious problem with your compressor. If the hissing noise is coming from your ductwork, then you may have leaking air ducts. This is annoying, but not necessarily a reason to worry. A hissing sound could indicate any of these things, but we’ll try to narrow it down a little more.

Does the hissing sound cease after a few seconds?

If you hear a hissing noise that stops after a few seconds, you may not have any problems. That can be refrigerant in your expansion valve, which is part and parcel of the normal operation of your HVAC mechanicals.

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 develops, you may notice a light hissing sound as the refrigerant escapes via the leak. Refrigerant escapes as a gas and can be a serious health concern. If you have signs of a refrigerant leak, shut down the unit and call a qualified HVAC company to come evaluate the noise.

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 help with the pressurization of the refrigerant gas and without repair, the leak will worsen. When it does, the hissing sound will often intensify, which can be a tell if you’re looking for the cause. You must maintain adequate pressure in your HVAC system for it operate correctly, 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 known as a condenser unit. Listen around here for the hissing noise. If you find the compressor is the cause, this could be a dangerous situation because it is an indication that the pressure within the compressor is too much. If you hear hissing, whistling, or shrieking coming from your compressor, power down your air conditioner immediately and call an HVAC technician.

AC compressor located in exterior condenser unit 

Compressors are some of the most expensive units to repair or replace inside an air conditioner. 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 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 components are installed and can’t be MacGyvered. While it’s impossible to provide estimates because of the variable costs, the bill is often large enough to consider a replacement in older ACs. 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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