Why is my AC making a hissing noise? 

A hissing noise inside your HVAC system is not something to be ignored. Among the possible causes are leaky refrigerant lines, an internal valve leak or a serious failure with your compressor. If the hissing noise is heard from your air ducts, then you could have leaking air ducts. This is annoying, but not necessarily a cause for alarm. A hissing sound may be a sign for 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 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 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 develops, you may hear a light hissing sound as the refrigerant escapes via the leak. Refrigerant escapes as a gas and can be a worrisome health concern. If you have signs of a refrigerant leak, turn off the unit and call a qualified HVAC company to come evaluate the noise. 

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 signal if you’re looking for the cause. You must maintain proper pressure in your system for it cool your home, and leaks 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 outdoor air conditioning unit, which is also known as a condenser unit. Listen around here for the hissing noise. If the compressor is the cause, this could be a hazardous situation because it is a sign that the pressure inside the compressor is too high. If you hear hissing, whistling, or shrieking coming from your compressor, shut off your air conditioner without delay and call an expert technician. 

Photo of AC unit showing location of compressor

Compressors are some of the most expensive units to repair or replace inside an air conditioner. Compressors are the part responsible for cycling refrigerant through the system. You cannot run an AC and cool your home sans compressor. The expense varies 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 another two stage compressor. It’s not possible to upgrade or downgrade the compressor type – your unit has specific requirements for what components are installed in order to operate safely. While it’s impossible to say how much a compressor replacement is because of the variable costs, the expense is often large enough to just do 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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