Should Car Be Running When Adding Freon?

Recharging your vehicle's air conditioner yourself can save you time and money. However, you need to make sure you do it properly, so should you leave it running when you add the freon? We have researched to answer this question in this article.

When adding freon, you will want to make sure the engine is running. In addition, you will need to have the air conditioner on with the fan on high. Leave the engine running and the A/C on maximum until you complete the freon add process.

Many car owners opt to add freon themselves; while it is a relatively simple procedure, a few things need to be done for your newly added freon to remain effective. In this article, we will discuss the process of adding freon to your vehicle. In addition, we will answer other frequently asked questions about freon, so read on!

A servicing car air conditioner, Should Car Be Running When Adding Freon?

Should Car Be Running When Adding Freon?

If you find that your vehicle's air conditioner is not cooling correctly, it might be time to add some freon. Adding freon yourself can save you the long wait times and high prices of hiring a mechanic, so it is something worth trying if yours fails on you.

Freon is a refrigerant used in air conditioners to cool down the air. It is a gas compressed into a liquid and then released into the air conditioner to help cool it down. This process allows you to use your air conditioner in the summer.

There are many different refrigerants, but car air conditioners use R-134a freon. This type of gas will help keep the temperature inside your vehicle cool when it is hot out. Unfortunately, this can be expensive to replace when you find that your system is no longer keeping you cool.

You should have your vehicle running when adding freon because the freon is added via a canister. Make sure that you hold this canister under your car and spray it into the outside system of the air conditioner.

Reasons to Keep Your Car Running

You should use your car's running engine and A/C when adding freon because:

  • Opening up the air conditioner's lines while not on will cause the freon to turn into a gas too quickly, causing your engine to run poorly or shut down.
  • It would be best if you kept the A/C running while adding the freon so that you can monitor how much you are putting in.
  • Running the car's engine with the A/C on high allows the freon to circulate faster.
  • Most cars now have electronics in their air conditioners that can be affected by the freon if it is not running at high speed.

When doing this process, be sure not to add too much freon. Over-filling your system can cause pressure build-up and lead to engine damage, so it is best to err on the side of caution when adding freon.

Like with any job, you must read the instructions on your can of freon before adding it to your vehicle. Pay close attention to the safety precautions included and make sure you follow them at all times while recharging.

Monitor tool on car engine ready to check and fixed car air conditioner system

How do I know if my car needs freon?

There are some tell-tale warning signs to watch for to know if your car needs freon.

automobile air conditioner freon can and test gauges under hood of car, Should Car Be Running When Adding Freon?

One of the most apparent signs that freon is low is if your air conditioner does not do as much as it used to. If your car's air conditioning unit is old, you will need to change out your components and recharge with freon until you can do so.

Other signs that you need to add freon to your vehicle include a warm air feeling from your vents even though the A/C is high.

Another common warning sign is refrigerant leaks coming from the car. If the vehicle leaks refrigerant, more than likely, it also needs freon.

Lastly, if you have ice on your compressor or coils, that is a sign that you need to add freon soon.

Will AutoZone Check your freon?

AutoZone has several locations that will check your freon for you. In addition, they will have a complete freon kit that you can purchase to recharge your A/C yourself. For this reason, AutoZone is an excellent option to add freon if you prefer to do things yourself.

Contact your local AutoZone for more information on having your freon checked. In addition, it is worth checking for a do-it-yourself freon kit just for a piece of mind. Typically, the kits will cost between $40 to $60.

Customer cars parked in front of AutoZone auto parts store

How do I add freon to my car?

Adding freon to your car is not something you should attempt if you are not very experienced. Because of this, it is usually best to have your local mechanic or shop add freon for you.

They must do this correctly because overfilling the system can cause damage and lead to leaks, which would require a more costly repair.

Steps for adding freon to your vehicle:

  1. First, turn the car on and turn the air conditioning to the highest setting with the fan high.
  2. Open your freon can and attach the dispenser.
  3. Open the hood of the vehicle and locate the low-pressure line. This will be the lowest point of the freon line, so it is a good indicator of where to start filling freon into your car.
  4. Add in your freon can's hose to the fill port on the vehicle and begin recharging, watching for any leaks, so you know where they are located at all times. Gently shake the can every once in a while to get more even distribution until you are done adding freon.
  5. Open the valves on the can to release the pressure.
  6. Keep your engine running and your A/C on maximum with the fan on high for a full fifteen minutes after you finish adding freon to ensure that it circulates completely through your entire vehicle's system.
  7. Turn the car off and remove the low-pressure hose from the fill port.
  8. Remove your gloves and throw them away before touching anything on your car so that you don't cross-contaminate them with oil or other types of lubricants on your gloves.
  9. Close all of the valves on your vehicle so that no freon can leak out.
  10. Close the cap to your low-pressure port, and then place the cap back onto your can of freon so that it does not mix with other cans in your garage. 
  11. After a day or two, you will need to recheck your car to ensure that your A/C is still running and cooling properly. If not, you may need to add more freon.


How long does it take to add freon to your car?

Young Mechanic Attaching Cables to Recharge Car with Freon

Depending on your experience adding freon to your car, the time it will take will vary. If you are comfortable around a vehicle, then the process may only take 30-45 minutes from start to finish.

If this is your first time adding freon to a vehicle, you can expect the process to take closer to an hour or more as you double-check and make sure that all of your work was done correctly.

Because having added too much or not enough freon will lead to poor performance and leaks in the system, you must double-check everything before turning your vehicle's A/C on.

It is also important to note that you should not drive the car until the air conditioning system has run for at least half an hour straight, with no signs of leaks in the existing system.

What happens if you put too much Freon in a car?

If you add too much freon to your car's system, it can create two potential problems.

First, it is possible for the engine to overheat because the compressor will not work at total capacity due to excess pressure in the system. If the vehicle doesn't overheat, it may idle roughly or even stall out or die.

Second, there is a possibility that one of your vehicle's parts may break if the excess pressure cannot escape quickly enough.

This will need to be repaired by a professional, as it could cause your car to break down on the road or leak more refrigerant into the air around you, which is dangerous for you and those driving nearby.

If you notice any of these symptoms, turn off your air conditioning immediately and get your car to a mechanic so you do not risk harming yourself or others.

Woman has car trouble

Final Thoughts

Adding freon to a car is not too complicated of a process, but it does require some attention to detail. However, anyone who has experience working on vehicles should have no trouble adding this refrigerant with no problems.

If you are not quite sure about your abilities or whether your air conditioning system needs recharging, consider hiring someone to do the job for you instead.

For more articles like this one, you should also check out:

How To Bleed Air Brakes On A Truck

What Happens If You Put Water In Your Car Oil?

How To Fix Spider Cracks In Car Paint

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