Why is my AC making a hissing noise? 

A hissing noise coming from your HVAC system is not something to be ignored. Among the possible causes are leaking refrigerant lines, an internal valve leak or a serious issue with your compressor. If the hissing noise is coming from your air ducts, then you might have leaky 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 a little 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 problems. That might be refrigerant in your expansion valve, which is a part 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 could indicate a refrigerant leak. If a refrigerant leak is present, you may notice a slight hissing sound as the refrigerant escapes through the leak. It escapes as a gas and can be a serious health concern. If you see signs of a refrigerant leak, shut down the AC and call a qualified HVAC company to come inspect the system. 

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 if unresolved, the leak will worsen. When it does, the hissing sound will often intensify, which can be a sign if you’re looking for a cause. You need to maintain adequate pressure in your HVAC system for it operate correctly, and any leak will create additional health and maintenance problems. It’s best to get this fixed post haste 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 around here for the hissing noise. If the compressor is the issue, this could be a dangerous situation because it is a sign that the pressure in the compressor is too great. If you hear hissing, whistling, or shrieking coming from your compressor, shut off your air conditioner without delay and call an HVAC technician. 

Photo of AC unit showing location of compressor

Compressors are some of the most expensive parts to repair or replace inside an AC unit. Compressors are the part responsible for cycling refrigerant through the system. You cannot power on an HVAC system and cool your home without a compressor. The cost is variable 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 another two stage compressor. It’s not possible to upgrade or downgrade the compressor type – your unit has specific requirements for what components 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 big enough to think about a replacement in older units. This is why it’s so important to shut off the air conditioning and call a trustworthy HVAC company if you hear hissing sounds coming from the compressor. 

Savings For You

See All Offers Here >
Offer

10% OFF FOR ACTIVE DUTY OR VETERANS

THANK YOU FOR YOUR SERVICE!

10% OFF Any Product or Service*
For all Active-Duty, Retired, and Veteran Military Personnel 

  • It’s our way of thanking you for your courage, dedication, and sacrifice to protect our freedom
  • All worked performed by licensed experts, and backed by a written, 100% Satisfaction Guarantee

Service Experts is proud to be affiliated with Military Makeover and Hiring Our Heroes

print
Offer

THREE LIMITED-TIME WAYS TO SAVE WITH AN ADVANTAGE PROGRAM BUNDLE

  • Bundle two HVAC systems through the Advantage Program and save $20 a month!
  • Bundle an HVAC and a Water Heater or Water Treatment System through the Advantage Program and save $15 a month!
  • Bundle a Water Heater a Water Treatment System or Indoor Air Quality through the Advantage Program and save $10 a month!

print

© 2025 Service Experts, Service Experts Heating & Air Conditioning, and the Service Experts logo and design are registered trademarks of Service Experts LLC and used under license by SE Canada Inc. All Rights Reserved. *Not applicable to the Advantage Program. See your signed Advantage Program Agreement for full details and exclusions. 100% Satisfaction Guarantee is subject to certain restrictions and limitations as set forth in the applicable Terms and Conditions.