Last Updated: 24.03.2022

For a comfortable driving experience, especially during the summer, your car needs an air conditioning system that works at its peak. If it stops blowing cold air and starts malfunctioning, it can be a sign of different issues, and one of the most common is low freon. 

Curious about the symptoms of low freon in a car? Clueless about the best solutions to fix the problem? Read on and learn from the insights we’ll be sharing. 

What Is Freon in a Car?

freon tank with test gauge


Freon is a popular brand of refrigerant gas. Also called R-22 refrigerant and HCFC-22, it was first introduced in 1930 as a miracle chemical. It is a mixture of carbon-hydrogen, bromine, fluorine, and chlorine. At room temperature, it is gaseous and has no smell or color. During compression, it turns into a liquid state, which is responsible for cooling a car. 

A non-flammable gas, freon goes through evaporation, which is like how a refrigerator works. A compressor in your car processes freon. After going through the compressor, the pressure rises. It becomes hot, moving through the coil. This is where it becomes liquid and flows through the expansion valve to cool down. After this, it goes through the filters and becomes cold air. 

Nonetheless, take note that not all cars have freon. It was phased out in 1994 because of its environmental impacts. It is deemed to be a danger to the Earth’s ozone layer, which is why better alternatives have been introduced. Nonetheless, if you have an old car, chances are, it is still using freon and not newer types of refrigerants. 

Symptoms of Low Freon in a Car 

Unsure if the problem originates from your car’s freon? Here are some of the signs that you should watch out for to confirm the cause. 

Warm Temperature

driver hands on aircon ventilator

One of the most obvious indications of a freon problem in your car is warm temperature. As soon as the AC starts blowing hot instead of cool air, then it is time to check the freon. You will start feeling the heat as you drive, urging you to open the windows instead. 

However, while the loss of cooling capacity can be a sign of low freon, it can be a symptom of other problems. For instance, it can be because of a faulty condenser, broken compressor, or damage to the electrical system. It can also be because you chose the wrong settings. 

Visible Leaks 

Open the hood and watch out for leaks. While you can blame other things, it is possible that you may be running out of freon. To be sure that it is freon, look for a thin and greasy substance. You will find it in the cabin, under the car, or around the compressor. Clean the leak as soon as you see it. If the problem persists, then you can confirm that it is an issue with the freon. 

Failure of Clutch to Engage

car airconditioner compressor

The AC clutch in your car allows the compressor to pressurize. If you turn on the cooling system of your car, you will notice that there is a clicking sound. This is what happens when the AC clutch engages. 

The main function of the AC clutch is to detect the level of freon that is present in your car. With this, the inability to engage means that you do not have enough refrigerant in the system, making it impossible for the compressor to function accordingly. 

Low Gauge Reading 

By looking at the AC gauge, you can easily determine if you have a freon problem to deal with. You will need a manifold gauge to confirm the reading and connect it to the parts of the system that delivers cool air. The red or high-side gauge should connect to the high-side service port. Meanwhile, the blue hose connects to the low-side pressure port. 

With the AC and the engine on, the static pressure should be anywhere from 80 to 105 psi. The high-side gauge reading should be from 200 to 300 psi while it must be 25 to 35 psi for the low-side gauge reading. If the reading is lower or zero, then it is a sign that the freon level is low. 

Bubbles in the Sight Glass 

Depending on the brand and model of the car that you are using, it might be equipped with sight glass. Look at it, and when you see that there is clear fluid flowing, it means that the freon is at an optimal level. However, when there are bubbles, then it shows that the freon is low. 

Ice on the Compressor 

As you inspect under the hood, one more thing that you should watch out for is the presence of ice in the compressor. This means that moisture is replacing the freon, resulting in ice.

When this moisture starts to freeze, there will be ice accumulation. 

How to Check the Freon in Your Car’s AC 

As soon as you experience the symptoms of low freon in the car, it is wise to confirm if it is indeed the problem. No need to rush to a local mechanic to do the job. Here’s how you can check your car’s freon level. 

Step 1: Start With an Inspection 

Before anything else, make sure that you are wearing safety goggles. Once your eyes are protected, open the hood and perform a quick inspection of the engine. Look for the low-pressure service port. You will find it between the evaporator and compressor. It is on the larger AC line. 

As you spot the service port, look for any sign of a problem. For instance, you might find loose clamps, which will require replacement. It is also common to find leakage. The latter is a serious problem, so it is best to consult with an expert who knows better. 

Step 2: Connect a Gauge 

At this point, you will need to put the gauge on the low-pressure service port. While the engine is running, connect the coupler to the port by taking the cap off and pushing the coupler. At this point, run the car’s AC at the highest possible level. 

Step 3: Let the Compressor Stabilize 

After connecting the gauge to the low-pressure service port, allow the compressor to cycle the pressure for a few minutes. This will be a chance to stabilize. Once it is stable, it is now time to take the measurement. The initial measurement will range from 25 to 45 psi. If the reading is too low, then it is a sign that your freon level is critical and should be replaced. 

How to Add Freon to Your Car 

Once you know that your car’s freon is at a dangerously low level, act immediately. Instead of paying someone to do the job, it can be an easy DIY task. 

  1. Connect the recharging hoses to the AC’s compressor system. Look for the shorter hose and attach it to the can that contains freon. 
  2. Open the can’s valve, allowing the air to purge from the system. After several seconds, squeeze the hose and tighten the valve. 
  3. Start the engine and turn the AC to the maximum possible setting. Open the valve on the low-side manifold, which will let the freon flow into the system gradually. While doing this, see to it that you are holding the can upright. 
  4. Once the can is empty, tighten the valve and take the hose off. Some freon can still be left in the can, so be careful when removing it. 
  5. Check the AC if it is already working properly. Otherwise, you might need to repeat the previous steps when the freon level isn’t sufficient. 


What happens when freon is low? 

A low freon level makes it impossible for the AC to produce cool air. Meaning, you will be uncomfortable inside the car, especially on a hot day. The cooling system will become inefficient as it runs without doing its purpose. 

Is it bad to run AC with low freon? 

Yes, it is bad to run your car’s AC once the freon is low. More than being inefficient, it can also put unnecessary strain on the engine and the other components that are responsible for the cooling system. It can result in a full system breakdown or expensive repairs. 

How much does it cost to replace a freon in a car? 

If you are going to do it yourself, you will need to buy a can of freon, which can cost anywhere from $50 to 120. Meanwhile, if you would rather have a pro handle the job for you, then prepare to pay anywhere from $180 to $260. 

Final Thoughts

Freon is a refrigerant in old cars that is responsible for the cooling system. When it is lower than the required level, you will be uncomfortable in your vehicle. As noted above, some of the most common symptoms of low freon in car include a warm temperature, leakage, inability to engage the clutch, low gauge reading, bubbles in the sight glass, and ice accumulation in the compressor.