Car Air Condition Problems? 10 Most-Common Issues & Fixes

Air conditioning was once thought to be a luxury in a car, but today it’s hard to find a newer car without it. You depend on it to keep you cool in the summer months.

When it doesn’t work, it makes driving far less enjoyable.

There are 10 main reasons air conditioning stops working, and we’ll cover each so you can keep your system in top condition.

 #1 – Your A/C System Has No Refrigerant

One of the biggest problems with your air conditioning system is that it can spring a small leak from a seal or a hose.

The system contains a refrigerant called Freon that is kept under high pressure, and when a small leak happens it will all leak out undetected.

How to Fix It

A leak in your air conditioning system is usually from a seal at connections or a hole in a hose. A leak can also occur from one of the main components like a condenser or evaporator, but a seal is the most common reason a leak occurs.

Once you detect that your air conditioning system doesn’t work well anymore, most of the refrigerant will have leaked out.

Cropped view of man touching car air conditioner

The first step in fixing a leak is to determine where it has occurred. You can add a dye to the air conditioning system and then check over the system to determine where the leak has occurred if it isn’t obvious.

Once the leak has been fixed, a qualified service center can evacuate the system of old refrigerant and refill the system with new refrigerant.

The system should be checked and recharged every 6-7 years by a qualified mechanic with the proper equipment.   

#2 – Your System Has a Faulty Pressure Switch

Your air conditioning system has two pressure switches that monitor the pressure inside the system. One is a high-pressure switch that is located after the compressor, and the other is a low-pressure switch located before the compressor.

Each monitors the system to ensure the pressure doesn’t go below or above a pressure threshold within the system.

If the pressure switches detect a problem or go bad, they will prevent your air conditioning system from cooling. You can press the button to turn the system on, but it won’t engage the compressor to pressurize the system.

How to Fix It

Many new cars will illuminate the Check Engine Light (CEL) if a pressure switch goes bad. Older cars may not, and you’ll have to diagnose the bad switch with a multimeter.

You can use the testing leads on a multimeter to verify the voltage between the terminals on the switches. One will be connected at the ground, and the others should have voltage at the terminal.

Once you have determined the switch that is faulty, you can evacuate the system and replace the switch. When the switch has been replaced, the system can be checked for leaks and refilled with new refrigerant.

#3 – Your A/C Compressor Clutch Won’t Engage

The belts that loop around the pulleys on your engine also drive the air conditioning compressor.

The pulley is attached to a clutch that engages to transmit the power from the pulley to the compressor to build pressure inside the A/C system.

If that clutch wears out, it will no longer transmit the power to turn the compressor and run the air conditioning system.

How to Fix It

The air conditioning compressor clutch may be able to be replaced on your car. It requires removing the pulley at a minimum and the large fastener holding the clutch onto the compressor.

Some compressors have shims between the clutch and the compressor shaft that can be removed for more contact between the components, and that may buy you a little more time with the current clutch.

New cars have started using a variable A/C compressor which doesn’t have a clutch to replace. In this case, the whole compressor unit must be replaced.

#4 – You Have a Faulty A/C Compressor

The A/C compressor has a main shaft that rotates and pressurizes the A/C system. The compressor has bearings that can fail, seals that can go bad, and it can drive metal shavings into the system that can damage other components.

If the compressor goes bad, it may not engage properly, and the system will blow warm air out of the vents.

Read Also: Car Won’t Start When AC Is On? (13 Solutions)

How to Fix It

Some A/C compressors can be rebuilt by a qualified mechanic, but most should be replaced with a new one if the original goes bad.

It requires evacuating the complete A/C system of refrigerant, replacing the compressor, and then flushing the system to ensure any contaminants are removed from the system.

Once it’s clean, it should be checked for leaks and then refilled with new refrigerant.

#5 – You Have a Damaged A/C Condenser

The A/C condenser transfers heat away from the air conditioning system, so it usually sits in a very exposed spot for maximum airflow.

Most cars have the condenser placed in front of the radiator, which means it can be hit with stones and debris while driving.

The fins on the condenser can be bent, which can reduce the amount of heat that can be dissipated by the condenser. It can also be damaged and cause a leak of the refrigerant.

How to Fix It

The condenser in most new cars is designed to be replaced in case of damage from rocks or debris. The fins can be straightened if they are bent, and the unit itself can be fixed if they are no longer available for replacement.

The A/C system should be evacuated of old refrigerant before the condenser is replaced, and then checked and refilled with new refrigerant when the work is complete.

#6 – You Have a Damaged Condenser Fan or The Fans Don’t Turn On

The A/C condenser is located in a place where it can be cooled with air passing through it. That requires movement of the car, so sitting at a stop light doesn’t cool the condenser well.

Your car has a fan to draw air through the condenser, whether it’s a unique fan for the condenser alone or the radiator fans. They should turn on when the A/C system is turned on to ensure the condenser has air always drawn through it.

How to Fix It

The fans should turn on when the A/C system is turned on. The easiest way to start diagnosing the problem is to turn the A/C system on and watch or listen for the radiator or condenser fans to also turn on.

You can do this without driving the car, but just have it running in your driveway. If the fans don’t turn on, the fans are either faulty or they aren’t being triggered to turn on.

The fans should have power to them when they are triggered to turn on. If they don’t turn on, you can use a multimeter to diagnose if voltage is being sent to the fans.

If there is no power, the relay could be bad or the A/C control unit could have gone bad. Check each component to determine which is the culprit and replace it when you find it.

The fans themselves can be replaced if they have gone bad or are damaged.

#7 – Your Belt Needs to be Replaced

The A/C compressor is driven by a belt on the engine. Some have a specific belt that only connects to the A/C compressor, while others have one main belt that drives all accessories like power steering and air conditioning.

These belts wear over time and develop cracks that can cause the belts to fail or lose the ability to turn the A/C compressor.

How to Fix It

The belts are replaceable, but it may take some effort to replace them. Some will be located behind other belts and accessories that will also need to be removed.

Once everything is out of the way, the belt can be replaced and every other component reattached.

#8 – You Have a Clogged Cabin Filter That Needs to be Replaced

The cabin filter is usually located behind the glovebox in your car, and it filters the incoming air to the passenger cabin. It will become dirty and block the airflow in your car.

You may notice that the air conditioning doesn’t cool your car as well in the hot months of summer, and the filter just needs to be replaced.

How to Fix It

The cabin filter is meant to be replaced frequently. Most will replace it annually on a specific holiday or at the start of the year.

The filter is easy to get to and doesn’t require expensive tools to complete the work. If you live in a dusty environment, you may need to replace the cabin filter more frequently than once per year.

#9 – You Have a Faulty Blend Door Actuator

The heat and cool air that comes into your car must be controlled so you only receive the right temperature. There is a door that moves in your air conditioning unit inside the car that directs the airflow, and it is controlled by an actuator that can fail.

How to Fix It

The blend door actuator may be driven by vacuum or electricity, but the function from car to car is the same.

It should move as you change the temperature from hot to cold on your air conditioning controls. You should be able to hear it moving inside the air conditioning unit inside the dash.

Before you try to replace the blend door actuator, ensure that the vacuum or voltage to it is still correct. Vacuum tubes over time can dry out and break.

Fuses can blow in the fuse box and prevent the actuator from working. If those are still OK, the actuator should be replaced.

Read Also: Do European Cars Have AC? (We Checked)

#10 – Your Heat Controller / Air Condition Control Unit is Faulty

The control unit sends the signals to the blend door actuator to change positions, to the A/C compressor to turn on, and to the fans to turn on to cool the condenser.

If it goes bad, part of the functions may not work anymore or the whole system may stop working.

How to Fix It

The control units are very well designed, but they aren’t foolproof. I suggest that before you have yours rebuilt or replaced, check all the other potential causes, and eliminate them as the reason your air conditioning isn’t working. They are expensive units.

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