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How to Put Freon in Car: An Easy to Follow Method

Is the air conditioning system in your car not as cold as it should be? A low level of refrigerant, also known as Freon, is the culprit in most cases. Just like a car tire losing its pressure over time, an AC system also loses charge during its lifetime. If the system is losing fluid, either for natural reasons or for a leak, you have to refill it. Do you know how to put Freon in car?

Why Freon Is Important for the AC System?

An air conditioning is a closed system. It exchanges heat from the inside of the car to the outside environment. How does it do this? With the help of the refrigerant.

There are two big surface areas where the system sends the gas through a circuit of tubes. These areas function like sinks that either send out or absorb thermal energy.

refilling car ac
The correct amount of Freon in the system is a must.

The refrigerant remains in a liquid form inside the AC system. But it absorbs the cabin heat and starts boiling at a point. Then, it evaporates into a gaseous form only to be condensed into the liquid state again. At this stage, the thermal energy from this transformation goes to the condenser before the radiator.

To have a fully functioning air conditioning, it must have the right amount of Freon in the system. An undercharged or overcharged system will result in poor performance.

How to Put Freon In Car: A Step-by-Step Process

If there is a leak in the air conditioning, you have to go to a mechanic. There are some rubber seals and O-rings that are likely to wear out over time. Topping up a leaked system is not going to work.

Things You Need

  • Refrigerant/Freon
  • A recharge hose with gauge
  • A thermometer

If you don’t have a recharge hose, try to borrow it from your local A/C supply shop or rent from somewhere.

Instructions for How to Put Freon in Car

Before topping up the AC system, park the car in a well-lighted and well-ventilated place. Also, wear a pair of protective goggles, thick waterproof gloves, and a long-sleeved shirt. Seek medical help immediately if the refrigerant touches your bare skin. It could cause frostbite in the affected area. Do not start the refilling process unless you have followed each of these safety measures.

Start the vehicle and the AC

Kick off the engine and increase the air conditioner’s coldness to the maximum level. Take the reading by putting a thermometer inside the vent. A normal reading at this stage will be 18 to 21°C.

You may instinctively try to put the back of your hand near the vent to see if it is cold. Don’t do that. It is likely to be biting cold.


Examine the compressor and clutch

Refilling Freon is necessary if the clutch is engaged at more than 21°C. But a not engaged clutch indicates a failed compressor, or too low level of refrigerant, or a not activated clutch.

Any compressor problem requires professional servicing and check the clutch’s connections and fuses if it is not working.

Hook up the hose.

Hook the refill hose to the low-pressure port. If you don’t know where it is, look around the exit path of the firewall. The port is likely to have a black or deep-gray cap or a cap with the letter ‘L’ on it. The hose will fit this port only, not the larger one (high-pressure port).

Take a gauge reading

The gauge attached to the hose will show the pressure reading of the air conditioning system.

With the clutch ON, less than 40psi reading means the AC is undercharged while more than 50psi indicates the opposite. In case of an overcharged system, release the excess refrigerant into an empty tank.

Refill with Freon

Refilling is an important step. To have the ideal refilling environment, make sure that the compressor and the engaged clutch are spinning, and the system vacuum is turned on.

If the Freon is in a tank, open the tank’s cap. If it is in an aerosol can, pull the trigger. Give a pause after a few seconds and then do it again. Keep doing this until the system is refilled.

how to put Freon in car
The cabin temperature should be 18 degrees Celsius.

Check the cabin temperature

Put the thermometer in front of the AC vent again and it should read 18°C now. If the temperature does not become colder than it was, you will need professional help to figure out the issue.

Learning how to put Freon in car is a useful maintenance tips to equip yourself with to save time and money with a mechanic.  More importantly, you will be able to timely and frequently provide your beloved vehicle with proper care in your own garage to ensure it will run smoothly without problems.