Why is my AC making a hissing noise?

July 25, 2019

A hissing noise inside your HVAC system is not something to be overlooked. Among the probable causes are leaking5 refrigerant lines, an internal valve leak or a serious failure 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 could be a sign for any of these things, but we’ll try to narrow it down further.

Does the hissing sound cease 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 operation of your HVAC unit.

Is the AC Making a Hissing Sound with Bubbling Noises?

Are you hearing a bubbling sound along with a hissing sound? This could indicate a refrigerant leak. If a refrigerant leak develops, you might hear 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 see signs of a refrigerant leak, power down your HVAC and call a expert HVAC company to come take a look.

If the issue is a valve leak, it should be repaired by a qualified technician 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 tell if you’re looking for the 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. It’s best to get this fixed post haste if possible.

Are Hissing Noises Coming from the Compressor?

The compressor is found in the outdoor air conditioning unit, which is also called a condenser. Listen quietly for the hissing noise. If it turns out that the compressor is the issue, this could be a hazardous situation because it is an indication that the pressure in the compressor is too high. If you hear hissing, whistling, or shrieking coming from your compressor, switch off your air conditioner without delay and call an HVAC technician.

AC compressor located in exterior condenser unit 

Compressors are some of the most pricey parts to repair or replace inside an air conditioner. Compressors are the part responsible for pushing refrigerant through the system. You cannot run an AC 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 now, you will 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 in order to operate safely. While it’s impossible to say how much a compressor replacement is because of the variable costs, the bill is often high enough to just do a replacement in older air conditioners. This is why it’s critical 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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