Hissing Noise from Car AC: Common Causes and Solutions

Car ac making hissing noise and not cooling

The comfort of a well-functioning car air conditioning system on a scorching day can be a true blessing. However, there are times when this essential feature of our vehicles can throw us a curveball in unexpected ways. One such issue that many car owners might encounter is the car AC making a hissing noise which indicates a problem in the air conditioning system. 

That said, here are the common causes and fixes of car AC making a hissing noise.

Causes of Car AC Making a Hissing Noise

A hissing noise from the car AC is not a major issue. However, if the problem persists, it is an indication of a malfunctioning part, causing car AC failure. 

Here are the common causes of a car AC making a hissing noise. Let’s go through them. 


A refrigerant, also known as Freon, circulates the cool air in the cabin. However, if there is a leak in the refrigerant lines, it will result in the car AC making a hissing noise. These leaks occur due to regular wear and tear and physical damage to the unit, causing small holes or broken seals. Also, due to such leaks, low refrigerant levels cause the car AC to blow hot air.


A bad car AC compressor is another reason for a hissing noise. When it is turned on, it will create unusual noises. A compressor may be affected by various factors such as overheating, lack of lubrication or clutch issues. Other mechanical and electrical problems such as imbalance of sensors or solenoids also affect the working of an AC compressor. As a result, car AC only works while driving.

car ac making hissing noise due to a bad compressor
Compressor issues disturb the working of the AC system, creating unwanted noises


The expansion valve in a car AC also called an orifice tube in some systems, regulates the refrigerant flow into the evaporator. From there, it undergoes a pressure drop, leading to cooling. If the expansion valve is stuck or damaged, it can cause pressure imbalances in the system, resulting in a hissing noise.


The evaporator and condenser are essential components for heat exchange in the AC system. If they become clogged with debris or dirt, it hinders the flow of refrigerant and creates abnormal sounds, including hissing.


A faulty condenser fan motor can disrupt the proper cooling process in the AC system. This leads to an imbalance in the refrigerant pressure and causes overheating. These issues cause the refrigerant to hiss as it circulates through the AC system. Besides, it is also one of the probable causes of weak airflow in car AC. 

hissing noise from the car ac due to bad  condenser fan
If the condenser fan motor doesn’t work, there will be a hissing noise and a weak airflow from the car’s AC


The internal valves in the car’s AC maintain the refrigerant pressure. If the internal valves are leaked, there will be no cold air. As a result, a hissing sound will be observed. 


When a car’s AC system is overcharged with refrigerant, it leads to excessive pressure inside the system. This pressure increases and causes the excess refrigerant to escape through small openings or the pressure relief valve. As the refrigerant tries to find a way to release the extra pressure, it creates a hissing noise, audible to the driver or passengers inside the car. 

ac making a hissing sound due to over charging
An overcharged AC system leads to a disturbance in the refrigerant pressure

Fixes of Car AC Making a Hissing Noise

We are now familiar with the potential causes of car AC making a hissing noise. Let’s explore different ways to fix this car AC issue.


The hissing noise from the AC will increase with time if the leaky valve is not changed. To so do, you can follow the steps mentioned below:

  • First, recover the remaining refrigerant from the AC system.  
  • Use UV dye or another appropriate method to locate the source of the leak in the AC system. Once identified, pinpoint the exact location of the leaky valve.
  • Carefully disconnect the refrigerant lines from the valve, leaving no refrigerant escapes during the process.
  • Obtain a replacement valve of the same type and specifications as the original one. Apply thread sealant or Teflon tape to the threads of the new valve, and then thread it into place by hand to avoid cross-threading.
  • Using the appropriate torque wrench, tighten the valve to the manufacturer’s recommended specifications. Be careful not to overtighten, as it may damage the valve or the surrounding components.
  • Reconnect the refrigerant lines to the newly installed valve and recharge the car AC system. 
  • Turn on the AC and check for any abnormalities in the cooling performance or any new leaks.


The condenser fan plays a crucial role in the AC system by dissipating heat from the refrigerant as it circulates through the system. If the condenser fan is not functioning correctly, it causes several issues that affect the overall performance and efficiency of the AC system. Therefore, it must be replaced at the earliest under professional guidance. 

fixes of car ac making hissing noise
Check for any leaks and make sure that the refrigerant levels are maintained


Certain car air conditioner leaks also lead to a hissing noise. When the low levels fall below a certain level, the refrigerant mixes with the system, causing unusual noises. Besides, There might be leaks in the AC system that allow the refrigerant to escape over time. Check common areas for leaks including hoses, fittings, seals, and the condenser.


Apart from the above-mentioned solutions, it is advised to get professional help. A car mechanic will be able to diagnose and treat the issue promptly, preventing any further inconvenience. Several car AC repair shops in Dubai, Abu Dhabi and other Emirates offer services to tend to these issues.

solutions for car ac making a hissing sound
Take your car to a mechanic for a prompt diagnosis

This wraps the causes and fixes of car AC making a hissing noise. You can also follow these car ac maintenance tips for keeping a check on your car in the scorching heat. Additionally, if you are in search of a new ride, go through these used cars for sale in the UAE that suit your preferences. 

Stay connected to dubizzle’s autos blog for more on car problems, maintenance and tips and tricks.