How to Recharge Your Car's Air Conditioner




Is the air coming from the vents in your car just not as cold as it used to be? You've likely run low on refrigerant in your A/C system.
Over time, tiny amounts of refrigerant leak from the lines, degrading A/C performance. The solution is simple - put more back in.

Recharging your air conditioner yourself is inexpensive and can be completed in just a few minutes. This is one of the most quick and easy tasks to perform when maintaining a vehicle, but holds the potential to cause problems with the air conditioning system if done incorrectly, so read each step very carefully before proceeding. When finished, your air conditioner should make icy cold air, and  the whole process should only set you back about  25-35 dollars and 15 minutes of your time.

This guide will contain information on how to recharge your air conditioner with refrigerant 134a or r-134a.

How Air Conditioners Work:
An air conditioner has three main parts. A condenser, a compressor, and an evaporator. The condenser and evaporator are, more or less, two radiators connected in a loop. The compressor is situated between them on one side of the loop. The system is sealed from the outside, and filled with a working fluid, in this case r-134a. The compressor takes low pressure, gaseous, r-134a, compresses it (which creates heat), then sends it to the condenser, where the heat is dissipated to the outside. After the condenser, liquid refrigerant travels to the evaporator, located inside the passenger compartment, where it is allowed to expand, removing heat and cooling the evaporator. The fan directs air over the evaporator, then out the air vents in your car.
Because the working fluid gets both very hot and very cold, it is important to keep moisture out of the system, as ice forming in the compressor can damage it.

As always, neither Instructables nor myself are responsible for any damage you may cause to yourself, your vehicle, or others.

Teacher Notes

Teachers! Did you use this instructable in your classroom?
Add a Teacher Note to share how you incorporated it into your lesson.

Step 1: What You Will Need and What You Should Know

First, was your car made before 1994? If so, your car likely uses R-12, and this guide isn't for you. However, if you search the engine bay and find a sticker stating that the system has been converted for use with r-134a, continue.

 - Two 12oz. cans of r-134a refrigerant ($9.99/ea)
 - One refrigerant dispenser ($16.00)
 - One pair of goggles

      Purchase the plain r-134a refrigerant from the bottom shelf. Don't be fooled by the shiny cans that have leak sealants and  performance enhancers. These are just "snake oil" and can actually harm your A/C system.

Refrigerant dispenser:
     Your dispenser needs to have both a pressure gauge and a trigger. These are not optional, and are required to do this safely and correctly. DO NOT purchase the dispenser/refrigerant combos.

Note: I do not endorse idQ, EZChill, or SpeedSteed  in any way. These are the parts that I happened to choose, and I am sure their competitor's products are just as good.

Step 2: Assemble the Dispenser

I would recommend putting on your goggles now.

Insert a can of refrigerant into bottom of the dispenser, and screw in all the way.

Note: There is a needle inside the dispenser that pierces the can automatically.

Step 3: Verify That the Compressor Is Running

1. Start the engine

2. Turn the A/C on

3. Turn the fan to maximum

4. Follow the hose from the low side fill port to a cylindrical device attached to the engine - this is the compressor

5. Locate the pulley on the compressor.

6. Is the center part of the pulley spinning?
Yes. Then the compressor is engaged, as it should be.
No.  Add half of a can of r-134a as detailed in the manner described in the upcoming steps. If the compressor still fails to engage, take your vehicle to a mechanic.

7. Leave the engine running and the A/C on maximum until you are finished with the entire filling process.

The photos depict the compressor in its engaged and disengaged states.

Step 4: Locate the Low Pressure Side Refrigerant Fill Port

1. Pop the hood.

2. Locate the refrigerant fill port on the low pressure side of the system. This will have a small plastic lid with an L printed on the top. Unscrew this cap to reveal the port.

Where is the fill port?
     For most vehicles, the low pressure side fill port is located on the left side of the engine bay. It will often be a small section of metal pipe that has two lengths of rubber hose coming off either end. Look to the back of the engine bay called the firewall. Protruding from the firewall should be two pipes or hoses next to one another, one larger than the other. Follow the larger hose to find the low pressure side fill port. The photos depict the location of the fill port on two different late model engines.

DANGER! Do not touch anything you are unfamiliar with. Almost everything in the engine bay moves and/or gets hot. The high pressure side (small) hoses get very hot, do not touch them. It is okay to touch the low pressure side hoses, they should be around ambient temperature.

Step 5: Attatch the Dispenser

Read and understand the following directions thoroughly. You will want to do steps 4-6 rather quickly.

1. Grasp the connector on the end of the hose thusly.

2. Lift the outer sleeve of the connector.

3. Squeeze the trigger for 2 seconds to purge the hose of any air.

4. While still squeezing the trigger and lifting the sleeve, press the connector firmly onto the fill port.

5. Release the outer sleeve of the connector, then the connector itself. It should snap into place on the fill port.

6. Release the trigger.

7. Gently tug on the connector to ensure it is properly seated on the fill port.

Squeezing the trigger keeps a constant flow of refrigerant coming out of the hose, purging it of any outside air and moisture, keeping them out of your air conditioning system.

Step 6: Recharge the System

Determine the correct pressure to fill to.
     Consult the table provided with your dispenser to determine the minimum and maximum acceptable pressure readings for the  current outside air temperature. This is your target pressure range. Some gauges have an adjustable "V' on them to highlight the acceptable pressure range. Set yours to the appropriate position now.

Take a pressure reading.
     If the needle on the dispenser reads below the minimum acceptable pressure, begin filling the system.

To fill the system with refrigerant:

1. Squeeze the trigger for 5-10 seconds, slowly tipping and shaking the can. NEVER TURN THE CAN UPSIDE DOWN.

2. Wait 30 seconds for the pressure to equalize.

3. Read the pressure displayed on the gauge again. Only measure pressure while the compressor is engaged. If the pressure is still too low, keep adding refrigerant in the manner described above.

4. When the pressure is correct, stop filing the system and wait a few minutes.

5. Check the pressure one last time before removing the dispenser hose and replacing the protective cover on the fill port.

       If you believe you have added too much refrigerant, consult the troubleshooting guide on the last step.

How do I tell when the can is empty?
     This sounds too simple, but, it will feel empty. Shake the can or strike it with your fingernail. If it feels like it's empty, it is.

How do I change cans?
     When the can is empty:
        1. Turn the can upside down.
        2. Hold the trigger on the dispenser for 30 seconds to 1 minute.
        3. Release the trigger.
        4. Unscrew the can from the dispenser, and screw a new one back on.
NOTE: You should leave the dispenser connected to the fill port while emptying the can, unless you are finished with the filling process.

DO NOT EMPTY THE LEFTOVER REFRIGERANT INTO THE AIR.Leave the unused portion in the can attached to the dispenser, and store where it will not be exposed to heat.

It is illegal under Section 608 of the Clean Air Act to knowingly vent refrigerants during any service, maintenance, repair or disposal of an appliance.

Step 7: Voila! You're Done.

If everything went as planned, your car's air conditioning should be ice cold! Enjoy.

If not, let's try to figure out where things went wrong:

The needle isn't moving/I don't think any refrigerant is going into the system.
     Be patient. It takes a fair amount of refrigerant to raise the pressure. If you still have issues, check to be sure that you connected the dispenser to the fill port properly.

Help! I think I put in too much refrigerant.
     Double check that the condenser hasn't disengaged. The pressure can spike quite a bit when the condenser disengages. If the pressure is still too high, I cannot recommend that you attach the dispenser to the fill port without a can and squeeze the trigger to release the excess refrigerant, because that is illegal.  You must take your vehicle to a mechanic.

The compressor won't engage!
     If your compressor will not engage, add half a can of freon. If it still will not turn, it is likely broken. Do not add more refrigerant! You will need a mechanic to repair this problem.

Be the First to Share


    • Furniture Contest

      Furniture Contest
    • Reuse Contest

      Reuse Contest
    • Made with Math Contest

      Made with Math Contest

    42 Discussions


    5 years ago on Introduction

    Hello my friend, before you recharge AC you need to remove air from the system with a vacuum pump, because humidity in the air can freeze inside ducts and damage them. Be careful.

    2 replies

    Reply 1 year ago

    Adding Refrigerant to a vehicle does not require a draw down (or evacuation) of the system. However if the system has a leak and has been repaired or if it has been open at some point then yes an evacuation definitely would be required and would best be taken to an A.C. mechanic, this is not for the untrained.


    Reply 3 months ago

    It does require to be evacuated before any repairs are made and then vacuumed down before refilling


    Question 1 year ago on Step 7

    I replaced my compressor. Standard practice is vacuuming the system.
    Do I need to get a vacuum on the A/C system? Or just filling it will work.

    1 answer

    1 year ago

    As an automotive technician i find this is a good write-up. However i need to make a few comments. When adding its always best to hold the can upside down since its a liquid refridgerant. Also adding refridgerant to an empty system is something that needs to be left up to the professionals as the system needs to be properly vacuumed down and kept under a vacuum until refridgerant is added. Overcharging a system can in fact blow it up. This process can in fact be very hazardous if done improperly and there are so many factors involved with the vehicles AC that can cause a properly charged AC system to not function correctly. If you dont know much about cars id suggest leaving this process up to the professionals.

    2 replies

    Reply 3 months ago

    I have a question . my ac was blowing hot air out, i was told it needed freon. I let someone put the freon in my car day before yesterday. While he was putting in a second a loud noise came from under the hood. Looked as though spraying from the connection of the freon can and instantly it looked like clouds of smoke coming from the opposite side under the hood. It was making this loud screeching noise. It stopped until earlier when i turned the ac on and smoke was coming from under the hood and the loud screeching until i turned it off... What did he do to it???


    Reply 3 months ago

    Its severely overcharged and he blew out a gasket or compressor pressure relief valve from my guess. This was one reason for my comment.


    Question 3 months ago

    I have a question . my ac was blowing hot air out, i was told it needed freon. I let someone put the freon in my car day before yesterday. While he was putting in a second a loud noise came from under the hood. Looked as though spraying from the connection of the freon can and instantly it looked like clouds of smoke coming from the opposite side under the hood. It was making this loud screeching noise. It stopped until earlier when i turned the ac on and smoke was coming from under the hood and the loud screeching until i turned it off... What did he do to it

    1 answer

    Answer 3 months ago

    He overcharged it and blew a gasket or the pressure relief valve on the AC Compressor from the sounds of it. This is one of the main reasons for my comment below


    Tip 7 months ago on Step 2

    IMPORTANT: The EZ fill refrigerant dispenser shown expects a single use can not a self sealing can. To use a self sealing can, you also need an adapter. Screw the adapter onto the dispenser first. Then screw the can to the adapter. Without the adapter, the can screws on but remains sealed.


    3 years ago

    Hello I have a 2003 Land Rover Freelander and I cant tell with valve to use to put the Cooling in. Both valve are the same size so I took them to auto avance and they were not able to figure out as well. Can you tell me what I need to know or how do I got by finding out without going to the dealer. Sorry if I use the word valve but I dont not know the right term.


    2 replies

    Reply 1 year ago

    Follow the lines from the compressor. The high pressure line will go towards the coolant radiator. The low pressure line will go to the passenger compartment.


    Reply 1 year ago

    If the AC works at all, it'll be the colder line that you want to add to.


    1 year ago

    refrigerant can cause harm to skin and eyes. wear mechanic gloves. DIY should be very careful. can/hose could explode in your hand. a low system may have a leak and not adding oil will cause damage to the compressor. if you don't have some knowledge of system this could be dangerous. utube has some vids on ac system.


    1 year ago

    This is really "topping off" an AC system, not "recharging". The term "recharging" makes me think of "recharging" the system after a major component replacement or repair, where it had to be totally "discharged". Modern AC systems have both an under pressure and an overpressure safety switch, either will cause the compressor to turn off. Sometimes they are combined into a single physical switch. You CAN "recharge" an empty system without vacuuming, but it won't work as efficiently as it should -- won't get as cold -- as it will have some air and moisture in it. The only way to remedy that situation is to empty and vacuum the system. Mositure "boils out" in a vacuum, so you get rid of both air and moisture when vacuumin. Vacuum pumps aren't cheap. Unless you plan on doing several it's not worth it to get a vacuum pump, take it to a pro.