Why is my AC making a hissing noise?

July 25, 2019

A hissing noise coming from your HVAC system is not something to be overlooked. Among the possible 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 might have leaking air ducts. This is annoying, but not necessarily something to panic over. A hissing sound may be a sign for 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 ceases after a few moments, you may not have any issues. That could be refrigerant in your expansion valve, which is a 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 develops, you might notice 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 see signs of a refrigerant leak, turn off the AC and call a expert HVAC company to come inspect the system.

If the problem 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 without repair, the leak will worsen. When it does, the hissing sound will increase, which can be a signal if you’re looking for the cause. You must maintain proper pressure in your HVAC system for it operate correctly, and refrigerant leaks cause additional health and maintenance problems. It’s best to get this fixed post haste if possible.

Are Hissing Noises Coming from the Compressor?

The compressor can be found in the exterior air conditioning unit, which is also known as a condenser unit. Listen around here for the hissing noise. If it turns out that the compressor is the issue, this could be a hazardous situation because it is a signal that the pressure within the compressor is too high. If you hear hissing, whistling, or shrieking coming from your compressor, turn off your air conditioner without delay and call an HVAC 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 cycling refrigerant through the system. You cannot turn on an air conditioner and cool your home without a compressor. The expense changes 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 a two stage compressor. It’s not possible to upgrade or downgrade the compressor type - your unit has specific requirements for what compressors are installed and can’t be MacGyvered. While it’s impossible to give a quote online because of the variable costs, the bill is often high enough to just do a replacement in older ACs. 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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