Why is my AC making a hissing noise?

July 25, 2019

A hissing noise inside your HVAC system is not something to 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 heard from your ducts, then you may have leaky 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 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 paired with a hissing sound? This could indicate a refrigerant leak. If a refrigerant leak is present, you may hear a light hissing sound as the refrigerant escapes through the leak. It escapes as a gas and can be a major health concern. If you see signs of a refrigerant leak, turn off the unit and call a professional 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 sign if you’re looking for a cause. You need to maintain adequate pressure in your HVAC system for it operate correctly, and refrigerant leaks cause additional health and mechanical problems. You want 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 unit. Listen nearby the condenser for the hissing noise. If you find the compressor is the problem, this could be an unsafe situation because it is an indication that the pressure in the compressor is too great. 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 costly parts to repair or replace inside an air conditioner. Compressors are the part responsible for pushing refrigerant through the system. You cannot run an AC and cool your home without a 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 impossible 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 provide estimates because of the variable costs, the bill is frequently high enough to consider a replacement in older air conditioners. This is why it’s so important 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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