When your car ac makes a hissing noise when turned on, it can be both disconcerting and concerning. Fortunately, there are some simple troubleshooting steps that can help you pinpoint the issue and resolve it. The hissing sound could be a sign of a leak or a problem with the expansion valve, compressor, or condenser. In addition, the hissing sound may also be due to a clogged evaporator or air filter.

Leaks in the air conditioning system are one of the most common causes of hissing noises. The hissing sound is created when the refrigerant moves from its high pressure side to the low pressure side through a series of valves and tubes.

If hissing is accompanied by the sound of shrieking and screeching, it could indicate a defective compressor or clutch. If left untreated, a defective compressor can cause catastrophic system damage over time.

One of the most effective ways to address a hissing sound is to perform a visual inspection and make sure there are no obstructions in the air vents. You can also try to straighten the AC condenser fins, which may be causing hissing noise due to restriction of airflow. Be careful not to apply too much force or you could damage the AC condenser.

If you can’t find the cause of the hissing sound, it’s best to have a professional from YourMechanic take a look at your vehicle. They can add refrigerant, use a dye to detect any coolant leaks and make repairs as needed.