Car A/C Making A Hissing Noise: Causes And Fixes

Car air conditioning system. Air condition switched on maximum cooling mode

Is your car A/C making a hissing noise? Rest assured, you’re not alone. It happens. But is it normal? That depends. If what you are hearing is refrigerant running through the A/C’s expansion valve when you first turn it on, that would be normal. If you shut your vehicle off and you hear a noise for a brief moment, that’s normal as well.

It could just be the noise of your air conditioner. But if it’s something you don’t recognize, a continuous hissing sound may point to a critical problem with your automobile’s air conditioning system.

Let’s take a look at what some of the causes for strange noises coming from your car A/C system might be attributed to.

The Pressure in Your Compressor Is Too High

Several problems could be indicated by high pressure in the compressor. It could be the result of a bad condenser fan motor, leaks in the evaporator, or an overcharged system.


  • You’ll have to find out which of the three causes is to blame before you can attempt a repair. You may need a technician for some of this.


  • Bad condenser fan motor – A technician can not only find this problem but take care of it by purging debris from the system.
  • Refrigerant leak – see “Leak in the Refrigerant Lines” below.
  • Overcharged system – The system’s pressure needs to be measured. Pressure will need to be released from the A/C if it’s above 30 psi.

Internal Valve Leak

This leak could start out slowly and then intensify as the hissing sound gets louder. More significant problems could arise if it’s not fixed right away.


  • Air conditioning simply will not happen if the refrigerant is not pressurized due to the leak.
  • The ” balloon method” is recommended by mechanics.


  • The valve needs to be replaced. You may need a mechanic if you don’t have the right kind of equipment.

A Leak in the Refrigerant Lines

As gas escapes, a hissing sound may be heard if one of the lines for refrigerant is leaking. Possibly, over time, a leak developed in a connection or metal part. It may also be as a result of a leak that can be attributed to O-rings, gaskets, hoses, and other rubber parts. The leak can come from the receiver dryer, accumulator, condenser, or evaporator.

Methods of detection:

  • A “sniffer”
  • A black light
  • Using soap solution
  • A visual inspection


  • Use “Super Seal” (be sure to follow the instructions for use of this product)
  • Replace/repair the evaporator

If Your Car A/C Is Making a Hissing Noise – We Have the Parts You Need

Where do you currently shop for your A/C parts and components? Before you turn to anyone else for the parts you need, check out all we have to offer at R&Y A/C Compressors. We stock condensers, accumulators, tubes, and the other parts and components  you need to work on the A/C system in your car.

To reach our customer service department, between 8:30 AM and 5 PM, Monday through Friday, please call 305-919-8864. On Saturdays, we are available from 8:30 AM to 2:30 PM. You may also choose to send us an email at [email protected].

If you’d rather, you can fill out our convenient online form, send it in, and we’ll send a response. We look forward to working with you.