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 probable 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 may have leaking air ducts. This is annoying, but not necessarily a cause for alarm. A hissing sound could be a sign for any of these things, but we’ll try to narrow it down further.

Does the hissing sound stop after a few seconds?

If you hear a hissing noise that ceases after a few seconds, you may not have any problems. 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 paired with a hissing sound? This could indicate a refrigerant leak. If a refrigerant leak is present, you might notice a slight hissing sound as the refrigerant escapes through the leak. The coolant escapes as a gas and can be a serious health concern. If you notice signs of a refrigerant leak, shut down your HVAC and call a qualified HVAC company to come take a look.

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 regulate 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 tell if you’re looking for a cause. You need to maintain adequate pressure in your HVAC system for it run as intended, and any leak will create additional health and maintenance problems. You want to get this fixed quickly if possible.

Are Hissing Noises Coming from the Compressor?

The compressor can be found in the exterior air conditioning unit, which is also called a condenser. Listen nearby the condenser for the hissing noise. If it turns out that the compressor is the issue, this could be an unsafe situation because it is a sign that the pressure within the compressor is too high. If you hear hissing, whistling, or shrieking coming from your compressor, turn off your air conditioner immediately 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 pushing refrigerant through the system. You cannot turn on an air conditioner and cool your home sans compressor. The expense is variable 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 impossible to upgrade or downgrade the compressor type - your unit has specific requirements for what compressors are installed and won’t accept substitutes. While it’s impossible to give a quote online because of the variable costs, the bill is frequently high 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.