Why is my AC making a hissing noise? 

A hissing noise inside your HVAC system should not be ignored. Among the potential causes are leaking refrigerant lines, an internal valve leak or a serious failure with your compressor. If the hissing noise is coming 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 stops after a few seconds, you may not have any problems. That could be refrigerant in your expansion valve, which is part and parcel of the normal operation of your HVAC mechanicals. 

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 presents itself, you may notice a slight hissing sound as the refrigerant escapes via the leak. Refrigerant escapes as a gas and can be a worrisome health concern. If you have signs of a refrigerant leak, turn off the AC and call a professional HVAC company to come evaluate the noise. 

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 if unresolved, the leak will worsen. When it does, the hissing sound will often intensify, which can be a signal if you’re looking for a cause. You need to maintain adequate pressure in your HVAC system for it operate correctly, 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 found in the outdoor air conditioning unit, which is also known as a condenser unit. 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 an indication that the pressure inside 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 a professional technician. 

Photo of AC unit showing location of compressor

Compressors are some of the most pricey parts to repair or replace inside an AC. Compressors are the part responsible for circulating refrigerant through the system. You cannot run an AC 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 your AC, 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 compressors are installed and won’t accept substitutes. While it’s impossible to give a quote online because of the variable costs, the receipt is often big enough to think about a replacement in older air conditioners. This is why it’s so important 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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