Adding Freon to Your Automobile's Air Condtioning System





Introduction: Adding Freon to Your Automobile's Air Condtioning System

About: Making or fixing things is how I relax.

Every automobile parts store I walk in these days has freon for sale. When R-12 was around I was licensed to buy and use it. I thought that was a good thing because you can be severely injured and or do $$ of damage to the system your working on. I decided I would do this instructable for the following 2 reasons . First to help people to understand and be safe. Second to equip you to make a repair to your AC system if it just needs a Freon charge to bring it back to good working order. First a few Rules you need to always follow.
1. Since your car engine is running to charge the AC system there are moving belts and pulleys,fan(s) and very hot parts. You can easily loose your fingers if you put them where they don't belong!
2. Freon if sprayed as a liquid on your body parts will freeze them instantly- FROSTBITE
3.Don't release freon into the atmosphere. It is not good for the earth.
4.Wear safety goggles at all times incase a hose blows or something goes wrong and freon is sprayed on your face.
5. If after reading this instructable you feel unsure about doing this then you should not be doing it.
Ok lets get started.
Tools needed:
1. The adapter to connect from the freon can to your freon SUCTION SIDE of the AC system.
Found where you buy freon.
2. Freon- probably 2 cans if your system is barely cold. If it is cool but not as cold as it was buy 1 can
3. A thermometer to see the temp drop from the dash vents or cold air out.
4. An AC system in need of some freon.

Step 1: Install the Hose on Can

We now make sure the pin in the tool is backed out so we cant see the point. We install the hose tool on the can. The can is not punctured. Once you screw the pin down into the can you can not remove the hose tool until the can is empty.When you screw the pin in to the can the pin seals in the freon. The other end of the hose also has a safety seat built in it so if the pin is backed out it will not vent freon to the atmosphere.
I spent a lot of time on this simple step but that was so you do this SAFELY.

Step 2: Familiarization With Your Cars Freon System.

First see what freon your vehicle uses. There should be a tag on the radiator cover cowl or somewhere under the hood that tells you. Look for 134A. If it says 12 this Instructable does not apply to you. There are conversion kits but that is beyond the scope of this demonstration. Now check out the pictures to see what the basic parts of an AC system are. Note that there are parts you can't see and we won't address those as they are not necessary to know about to charge the system .
The basic AC system has a pump or compressor that pumps a low pressure gas to a high pressure. That is why it is called a compressor. Next the high pressure gas goes to a condenser that sits infront of your radiator. You might of noticed your fan runs a lot when the air conditioning is on. That is so cool air is pulled through the condenser to cool the hot compressed freon. Next a wonderful thing takes place. The hot freon after being cooled turns from a hot gas to a semi hot liquid. Trust me on this. The liquid is still at high pressure and very warm and stays that way until it is used to make the evaporator cold.
Once it travels into the evaporator it is now a low pressure cold gas again and not a liquid. It then leaves the evaporator and goes through hoses to the accumulator / drier which is just a big tank to catch any liquid that might of snuck out with the gas. Then from there the low pressure cold gas goes back into the compressor to start the cycle all over again. You may of noticed the system has a high pressure side and a low pressure side-VERY IMPORTANT. You will only work on the LOW PRESSURE SIDE. The freon is added on the LOW PRESSURE SIDE ONLY. The hose tool you bought is made so you can only hook to the low side as the high side and low side fittings are different sizes and shapes for SAFETY'S SAKE.

Step 3: Hooking Up the Freon

Remove the SUCTION SIDE port cap. This can be in a number of places on your car so you may need to look for it. It will always be on a bigger tube. By that I mean the high pressure side tubing is smaller diameter than the low pressure side. Thankfully the ports are not interchangeable so you can't plug on the wrong port. The air in the line is vented now by loosening the fitting (see pictures)
Then retightend and The can punctured by screwing in the pin until it bottoms.
Now start the car and turn the AC or climate control to high and the fan on high.
Make sure the temperature control is at full cold or set it to the lowest temp you can if it has numbers.
Now we are ready to charge the system.

Step 4: Charging the System

You now start the car with the AC system on high. You open the can tap so freon starts to travel from the can to the suction side. You only need to open the can tap 3 to 4 turns and you will feel the top of the tool getting cooler. This tells you the can is open enough. Don't try to unscrew it all the way to make it go faster as the needle can be screwed out of the can tool and then you have a fountain of freeze spraying all over- not good. Freon moves from the can to the suction side because the can is under low pressure but the suction side is under even lower pressure so the freon leaves the can and moves to the system. Now watch the accumulator can. If you can safely touch it you will see it's warm if your low on freon. As you charge the system it will become cooler. Finally it will start to sweat. That is when you stopAdding freon. Now you have about the right amount. If you add too much your over stressing the system and it is not going to work any better in fact it will not be as efficient. Overcharging also adds stress to the system since pressures are higher than normal. So now that the accumulator is sweating close the can tap. Check the temp in the car and you should feel very cool air . I dropped from 87 to 50 degrees with a can and 1/2 of another. The cans come in preset quantities. I don't ever buy the large completely charge your system can as it is usually too much. The smaller cans are what you need. I don't recommend the sealer in a can. If you think you need to add oil to your system take it to a shop so its done correctly. Any left over freon do not vent to the atmosphere. tighten down the can tap and leave the tool on the can. You can tell when a can is empty as if you shake it it will feel empty.
Close the tap before you remove the hose off of the fitting. Then recap the fitting. If your system does not work properly ( no cold air ) it is time to go to a pro. Open freon can be used at a later date but must be stored in a cool place That is CHILDPROOF. The temperature coming out of your vent can vary depending on a lot of factors so don't think you have to see the temperatures I saw.

Step 5: Final Thoughts

As you can see in the photos we dropped 30 degrees and it actually went down to 51 degrees. Good enough.
A recap:
Charge the system with the can upright position. By the way it can take up to 1/2 hour to charge a system...
If your system is very low when you start putting in freon the compressor may not start turning until a sensor sees you have a predefined minimum amount of freon. Add 15 minutes more for charging. This is a safety so you don't damage the freon compressor...
If you see oily goo all over your compressor or at a line fitting don't bother charging it as it needs pro service or your shooting your wallet in the foot in the long run...
If after you charge your system the cold air comes and goes and comes and goes you have moisture in the system and it needs to go to a pro...
If things don't seem to be working as I have described in this topic then something else is wrong and you need to have a trained pro look at it...
Remember a pro uses gauges to check pressures on the high and low pressure sides. He factors in ambient air temp and even humidity levels and he can pinpoint complex problems like that. We used the >watch the symptoms< process to determine we are in the ball park in terms of the amount of freon we have in our system. My feeling is a little low is way better than too much...
After your all done check the port cap to see its in place. Put your tools away. Go for a nice cool ride. If it all works ok go look in the mirror and say. I DID IT AND PAT YOUR SELF ON THE BACK FOR A JOB WELL DONE!



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    I just put freon on my Toyota RAV4 put now the air is not coming cold ! The last time I did it was more than 2 years ago and I just wanted to recharge but I think I don't know ! Did I put to much ? The more u put the more cold the air is gonna be? How does it work ? Now is worse than before ! I use to have cold air but not like when I bought the car in 2007 n like the last time I recharge was 2 years ago but with the wheater conditions in fl I thought it was time to do it again

    Not trying to be petty, however "Freon" was just a brand name used by the DuPont corporation. The appropriate term to call such substance would be "Refrigerant". The term refrigerant can refer to all the different types such as R-12, R-22, R-134a etc.(and many more). But most importantly true Freon is composed of chlorofluorocarbons.

    4 replies

    Your right.
    My intended audience for this was folks who wanted to get their system going but really did not understand what was going on behind the scenes. Nine times out of ten if you walk into a parts store and ask the counter guy "I need some of that stuff that makes your AC cold" The guy will say "you mean freon and its over there." Freon is the accepted street name if you will and most people recognize That name. Take a look at this big chain auto parts seller's web page and see how they identify refrigerant on their web site,101308/shopping/accessoriesLanding.htm

    Yes, I see your point, but that is not right. Not even for large corporations, unless it is manufactured by DuPont, but even they don't call it that anymore. Not picking on you, but maybe someone could make a buck or two by letting DuPont know someone is "ripping off" (using without permission) their trade name. Like for example if you invented the "Gort" recharger, and someone else marketed a similar product, and called it a "Gort" ... you should get millions due to inventors rights and copyrights... but maybe now I'm just being silly. But someone out there should offer their legal services to DuPont against "un-named big name auto parts store" hint hint... if anyone does this, keep Patsy001 in mind for compensation of his idea.

    kInda lIke a phillips screwdriver (crosspoint) or a frigidare (refrigerator)? we all do it. its a normal way of communication outside of the english classroom.


    It's your idea ..have at it

    And to remove your refrigerant you have to take it to a shop they will recover it then vacuum your system out technically if you just crack the line and let it bleed out you can be facing up to a 30g fine if you get caught but a little bit escapes that's fine it's called a diminamous release

    1 reply

    de minimis release and that's only for purging your lines of air and when you disconnect your hoses.

    If you have a low loss fitting on the liquid line (hi side) it prevents all the liquid in your gauges from spraying out when disconnecting. You will want to open the hi side after disconnecting if you have a low loss fitting so it doesn't mess up your calibration.

    Knowing venting refrigerant into the air is a $37,500 fine if your caught and a felony.

    Adding to much freon is possible and actually diminishes the performance of your A/C system. There are other reasons why your A/C might not be working like either one of the coils being dirty prevents the transfer of heat. We use terms such a sub cooling and super heating in the field to determine potential causes for problems.

    This is only a band-aid on a potentially worse situation. The A/C system is a closed system and the refrigerant does not wear out or go bad unless it is contaminated. If it is contaminated, then you have a leak in the system. A leak needs professional service. You can put new refrigerant in all day, and ultimately, it will become contaminated. While this seems like a nice "pat yourself on the back" situation, it ultimately could mean costlier repairs on your vehicle.

    I got a 2006 lariot f-150 truck I just recently added Freon to where it supposed to be at. now the ac codenser kicks on when the car is started the lines sweat cold but when u go inside the trick the air still blows hot. Any suggestions or any ideas of what could cause this? plz email me at if u can Thx.

    Don't put r134a in a 1967 car it most likely takes r12 which can be hard to come by check for a tag under the hood which it probably won't be there so try looking on the only way you could put r134a in is if you had the system updated which can be pricy and thank god for patsy001 it gets irritating here people call every refrigerant freon and and it's surprising to here someone actually know about the molecular break downs

    How much 134A is needed in a 1967 Camaro 327? Thanks. Phil

    How would I be able to remove A/C from a car?

    Hey, you did a gret job on this ible. Five Stars! I was intimidated by A/C systems until a couple of years ago. I had to make a trip to New Orleans (in August!) and my Suburban's A/C had just crashed (compressor). I had one day to figure it out or burn up. Necessity is the mother of A/C repair!

    2 replies

    Thanks. Good for you for not giving up and figuring it out. Don't things just pick the worst time to break?

    I know...the brakes on our VW failed right when we were about to go home which was 50m away...had to take it to two service stations because one didnt have the part.

    NEVER;EVER touch the fan if its not unplugged.I have seen cars that are off and still have the fan running full blast.


    As a side note you can dust talcum or baby powder onto the accumulator and then easily watch for moisture accumulation on it.

    Is there a concern about accidentally putting moisture in the system when you recharge it?

    1 reply

    Moisture will cause freezing of your system. Usually at the expansion valve which is where the freon escapes high pressure into low pressure through a tiny orifice. Moisture likes to freeze that orifice closed. It will unfreeze in about 10 minutes and your ac will work again. 134A boils around -15 degrees F. So its very cold at the expansion valve and that is why you don't want moisture. The oil in the compressor also likes to absorb the moisture and this can cause it to go acid over time.All AC systems have a "drier" in them. That is a powerful chemical that absorbs and holds any moisture. If you accidentally allow moisture in your system most likely there will be absolutely no problem because the drier will immediately grab it. But I wanted everyone to know the correct procedure. The quick answer to your question is don't lose any sleep over it. In my summary you noticed I stated that if after you charge your system it goes from cold to warm over and over its probably moisture. Remember that when an AC system is recharged by non pros they have no way of knowing if their system is moisture saturated or not. On older cars there was a little view window on top of the receiver / drier and if it was blue you were good if it turned pink you were moisture saturated. If you have a leak and lose ALL your freon then the drier will actually pull" outside of the system" moisture in through the leak path and saturate itself. Then when you Recharge it there is moisture mixed with freon and that is a major problem in terms of it working as it should.