Why is my AC making a hissing noise?

July 25, 2019

A hissing noise coming from your HVAC system is not something to be ignored. Among the possible causes are leaky refrigerant lines, an internal valve leak or a serious issue with your compressor. If the hissing noise is heard from your air ducts, then you might have leaking 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 stop after a few seconds?

If you hear a hissing noise that ends after a few seconds, you may not have any problems. That can be refrigerant in your expansion valve, which is a 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 notice a light hissing sound as the refrigerant escapes from the leak. It 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 technician as soon as possible. The job of the valves is to manage the pressurization of the refrigerant gas and without repair, 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 adequate pressure in your system for it cool your home, and leaks create additional health and mechanical problems. It’s best to get this fixed post haste if possible.

Are Hissing Noises Coming from the Compressor?

The compressor is located in the outdoor 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 a hazardous situation because it is an indication that the pressure within the compressor is too great. If you hear hissing, whistling, or shrieking coming from your compressor, switch off your air conditioner pronto and call an expert technician.

AC compressor located in exterior condenser unit 

Compressors are some of the most expensive units to repair or replace inside an AC. Compressors are the part responsible for cycling refrigerant through the system. You cannot turn on an air conditioner and cool your home sans 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 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 and can’t be MacGyvered. While it’s impossible to say how much a compressor replacement is because of the variable costs, the expense is often high enough to consider a replacement in older ACs. 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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