Why is my AC making a hissing noise? 

A hissing noise coming from your HVAC system should not be disregarded. Among the probable causes are leaking refrigerant lines, an internal valve leak or a serious failure with your compressor. If the hissing noise is originating from your ducts, then you may have leaky air ducts. This is annoying, but not necessarily a cause for alarm. A hissing sound may indicate 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 moments, you may not have any issues. That might be refrigerant in your expansion valve, which is a part of the normal day to day 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 is present, you may notice a slight hissing sound as the refrigerant escapes via the leak. Refrigerant escapes as a gas and can be a worrisome health concern. If you notice signs of a refrigerant leak, shut down the AC and call a professional HVAC company to come inspect the system. 

If the problem 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 left alone, 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 need to maintain proper pressure in your system for it cool your home, and any leak will create additional health and mechanical problems. You want to get this fixed quickly if possible. 

Are Hissing Noises Coming from the Compressor? 

The compressor is found in the exterior air conditioning unit, which is also known as a condenser. Listen quietly for the hissing noise. If the compressor is the problem, 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 HVAC technician. 

Photo of AC unit showing location of compressor

Compressors are some of the most pricey units to repair or replace inside an air conditioner. Compressors are the part responsible for circulating refrigerant through the system. You cannot power on an HVAC system and cool your home without a compressor. The cost changes based on factors like the type, unit size, and brand requirements. If you have a two stage compressor now, you would need to replace it with another 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 say how much a compressor replacement is because of the variable costs, the bill is frequently 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 reputable HVAC company if you hear hissing sounds coming from the compressor. 

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