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 probable causes are leaky refrigerant lines, an internal valve leak or a serious problem with your compressor. If the hissing noise is heard from your air ducts, then you may have leaky air ducts. This is annoying, but not necessarily a cause for alarm. A hissing sound could be a sign for any of these things, but we’ll try to narrow it down a little more.

Does the hissing sound end after a few seconds?

If you hear a hissing noise that ends after a few seconds, you may not have any issues. That might 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 could indicate a refrigerant leak. If a refrigerant leak develops, you might hear a light hissing sound as the refrigerant escapes through the leak. It escapes as a gas and can be a worrisome health concern. If you notice signs of a refrigerant leak, turn off the AC and call a expert HVAC company to come inspect the system.

If the issue is a valve leak, it should be repaired by a professional as soon as possible. The job of the valves is to regulate the pressurization of the refrigerant gas and without repair, the leak will worsen. When it does, the hissing sound will sometimes grow louder, which can be a tell if you’re looking for the cause. You need to maintain proper pressure in your system for it operate correctly, and leaks create additional health and maintenance problems. You want to get this fixed post haste 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 unit. Listen around here for the hissing noise. If you find the compressor is the issue, this could be an unsafe 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, switch off your air conditioner immediately and call an expert technician.

AC compressor located in exterior condenser unit 

Compressors are some of the most pricey parts to repair or replace inside an air conditioner. Compressors are the part responsible for pushing refrigerant through the system. You cannot power on an HVAC system and cool your home sans compressor. The expense 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 will 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 can’t be MacGyvered. While it’s impossible to give a quote online because of the variable costs, the expense is often big enough to consider a replacement in older ACs. This is why it’s critical to shut off the air conditioning and call a reputable HVAC company if you hear hissing sounds coming from the compressor.

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