Why is my AC making a hissing noise? 

A hissing noise coming from your HVAC system is not something to be disregarded. Among the probable causes are leaking refrigerant lines, an internal valve leak or a serious problem with your compressor. If the hissing noise is heard from your ducts, then you might have leaking air ducts. This is annoying, but not necessarily a cause for alarm. A hissing sound could indicate any of these things, but we’ll try to narrow it down a little more. 

Does the hissing sound cease after a few seconds? 

If you hear a hissing noise that ends after a few moments, you may not have any problems. That could be refrigerant in your expansion valve, which is part and parcel of the normal day to day operation of your HVAC mechanicals. 

Is the AC Making a Hissing Sound with Bubbling Noises? 

Are you hearing a bubbling sound along with a hissing sound? This may indicate a refrigerant leak. If a refrigerant leak presents itself, you may hear a light hissing sound as the refrigerant escapes through the leak. It escapes as a gas and can be a serious health concern. If you have signs of a refrigerant leak, turn off the AC and call a professional 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 manage 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 signal if you’re looking for the cause. You need to maintain proper pressure in your HVAC system for it run as intended, 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 can be found in the exterior air conditioning unit, which is also called a condenser. Listen quietly for the hissing noise. If it turns out that the compressor is the problem, this could be a dangerous 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, shut off your air conditioner pronto and call an expert technician. 

Photo of AC unit showing location of compressor

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 power on an HVAC system and cool your home sans compressor. The pricing is variable based on factors like the type, unit size, and brand requirements. If you have a two stage compressor in your AC, you will need to replace it with another two stage compressor. It’s not possible 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 say how much a compressor replacement is because of the variable costs, the bill is often high enough to think about a replacement in older ACs. This is why it’s critical to shut off the air conditioning and call a trustworthy HVAC company if you hear hissing sounds coming from the compressor. 

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