Why is my AC making a hissing noise?
A hissing noise inside your HVAC system is not something to be ignored. Among the possible causes are leaking5 refrigerant lines, an internal valve leak or a serious issue with your compressor. If the hissing noise is heard from your ductwork, then you might have leaking air ducts. This is annoying, but not necessarily something to panic over. A hissing sound could 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 stops after a few moments, you may not have any issues. That could be refrigerant in your expansion valve, which is part of the normal 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 may indicate a refrigerant leak. If a refrigerant leak is present, you might 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 notice signs of a refrigerant leak, power down your HVAC and call a qualified HVAC company to come take a look.
If the problem is a valve leak, it should be repaired by a professional 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 sometimes grow louder, which can be a tell if you’re looking for the cause. You need to maintain proper pressure in your system for it run as intended, and refrigerant leaks cause additional health and mechanical problems. You ought to get this fixed post haste if possible.
Are Hissing Noises Coming from the Compressor?
The compressor is located in the exterior air conditioning unit, which is also known as a condenser. Listen quietly for the hissing noise. If you find the compressor is the issue, this could be a dangerous situation because it is an indication that the pressure within the compressor is too much. If you hear hissing, whistling, or shrieking coming from your compressor, turn off your air conditioner pronto and call a professional technician.

Compressors are some of the most costly parts to repair or replace inside an air conditioner. Compressors are the part responsible for circulating refrigerant through the system. You cannot run an AC and cool your home sans compressor. The expense is variable based on factors such as 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 compressors are installed and won’t accept substitutes. While it’s impossible to say how much a compressor replacement is because of the variable costs, the receipt is frequently high enough to consider a replacement in older air conditioners. This is why it’s crucial to shut off the air conditioning and call a trustworthy HVAC company if you hear hissing sounds coming from the compressor.