Why is my AC making a hissing noise?

July 25, 2019

A hissing noise inside your HVAC system should not be overlooked. Among the potential causes are leaking5 refrigerant lines, an internal valve leak or a serious issue with your compressor. If the hissing noise is coming from your ductwork, then you might have leaking air ducts. This is annoying, but not necessarily something to panic over. 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 ceases after a few seconds, you may not have any issues. That might be refrigerant in your expansion valve, which is part and parcel 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 along with a hissing sound? This can indicate a refrigerant leak. If a refrigerant leak presents itself, you may hear a light hissing sound as the refrigerant escapes from the leak. Refrigerant escapes as a gas and can be a serious health concern. If you have signs of a refrigerant leak, shut down the unit and call a expert HVAC company to come evaluate the noise.

If the issue 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 if unresolved, the leak will worsen. When it does, the hissing sound will sometimes grow louder, which can be a signal if you’re looking for a cause. You must maintain adequate pressure in your HVAC system for it run as intended, and any leak will create additional health and mechanical problems. You want 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 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 in the compressor is too great. If you hear hissing, whistling, or shrieking coming from your compressor, switch off your air conditioner immediately and call an HVAC 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 circulating refrigerant through the system. You cannot power on an HVAC system and cool your home without a compressor. The pricing changes 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 impossible to upgrade or downgrade the compressor type - your unit has specific requirements for what parts are installed and can’t be MacGyvered. While it’s impossible to provide estimates because of the variable costs, the expense is often high enough to just do a replacement in older air conditioners. This is why it’s crucial 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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