Why is my AC making a hissing noise? 

A hissing noise inside your HVAC system should not be overlooked. Among the possible causes are leaky refrigerant lines, an internal valve leak or a serious issue with your compressor. If the hissing noise is coming from your ducts, then you could 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 end after a few seconds? 

If you hear a hissing noise that stops after a few seconds, you may not have any issues. That could be refrigerant in your expansion valve, which is part of the normal day to day operation of your HVAC system. 

Is the AC Making a Hissing Sound with Bubbling Noises? 

Are you hearing a bubbling sound paired with a hissing sound? This may indicate a refrigerant leak. If a refrigerant leak presents itself, you may hear a slight 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, shut down the AC and call a qualified HVAC company to come evaluate the noise. 

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 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 a cause. You must maintain adequate pressure in your HVAC system for it cool your home, and leaks create additional health and mechanical problems. You ought 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 problem, this could be a hazardous situation because it is a sign that the pressure in 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. 

Photo of AC unit showing location of compressor

Compressors are some of the most costly units to repair or replace inside an AC unit. Compressors are the part responsible for pushing refrigerant through the system. You cannot turn on an air conditioner and cool your home sans compressor. The cost varies based on factors like 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 components are installed and won’t accept substitutes. While it’s impossible to give a quote online because of the variable costs, the receipt is frequently large 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 reputable HVAC company if you hear hissing sounds coming from the compressor. 

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