Why is my AC making a hissing noise?

July 25, 2019

A hissing noise coming from your HVAC system should not be overlooked. Among the potential causes are leaky refrigerant lines, an internal valve leak or a serious problem with your compressor. If the hissing noise is originating from your ducts, then you might have leaky 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 further.

Does the hissing sound cease 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 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 along with a hissing sound? This can indicate a refrigerant leak. If a refrigerant leak presents itself, you may hear a slight hissing sound as the refrigerant escapes through the leak. The coolant escapes as a gas and can be a worrisome health concern. If you have signs of a refrigerant leak, power down the AC and call a expert HVAC company to come take a look.

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 help with the pressurization of the refrigerant gas and left alone, 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 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 located in the outdoor air conditioning unit, which is also called a condenser. Listen quietly for the hissing noise. If you find the compressor is the problem, this could be an unsafe situation because it is a sign that the pressure inside the compressor is too much. If you hear hissing, whistling, or shrieking coming from your compressor, shut off your air conditioner pronto and call an expert technician.

AC compressor located in exterior condenser unit 

Compressors are some of the most expensive parts to repair or replace inside an air conditioner. Compressors are the part responsible for pushing refrigerant through the system. You cannot turn on an air conditioner and cool your home without a compressor. The expense changes based on factors such as the type, unit size, and brand requirements. If you have a two stage compressor now, you would need to replace it with a 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 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 reliable HVAC company if you hear hissing sounds coming from the compressor.

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