How to Recharge Your Car's Air Conditioner





Introduction: 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.

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.



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    Please be positive and constructive.


    2 Questions

    Installed new compressor, however Freon will not go in.

    Auto-Zone & my helper do not know why . 2005 trailblazer.

    Can you help ………… R. Wehr

    Will r-134a work with a 2004 Ford F150 Heritage?


    Note this is for some countrys only .

    This is no way is legal in Australia , you can buy cans like that . Gas also cost 200 dollars per kilo here.

    134a is in 90% of fridges . but you need a different connection sometimes you cant even access the system . you also have a real high chance of over charging or getting the wrong charge in it.
    I suggest no one attempts DIY fridge repairs.

    1 reply

    200 dollars?? Must be some green government tax.

    Here in 'some country' in this case in the US ~ 5 Dollars per pound, or 10 Dollars per kilo.

    You mention you need a dispenser with a gauge & trigger, & follow up with a strong warning to not purchase the refrigerant/dispenser combo, but fail to provide any explanation or reason as to why not... Why should we not purchase a refrigerant/dispenser combo with a gauge & trigger?

    1 reply

    I didn't write this Instructable, and so I don't know if there are other reasons, but this would be my reasoning: If your gauge and trigger assembly is fixed to the can, then you couldn't use them again for another application. But if they are separate, you don't just throw them away when the can is empty. Less waste and better economy.

    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.


    Thank you for this. With your instructions I was able to add refrigerant to my '06 Dodge Durango, and in about 20 minutes I had cold a/c again. An absolute necessity for summers in the Bahamas.

    I think on the last page you used the words condenser when you meant compressor. When the compressor disengages the pressure on the low side can get quite high.

    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.

    Also tfellad is right -- overcharging is just as bad as undercharging.

    I can't believe that this summer nearly every state has reached 90 degrees at some point, especially in the northeast! I live in Florida so I'm used to the temperatures to a certain degree (ha), but this year has been especially hot. And to top it all off my car AC just did not seem to be blowing as cold as it did last year. I had it checked out by a mechanic friend and they said it was fully charged, so there was nothing they could do. Luckily, I came across this new product called QuickCool AC and gave it a try. Once we added it to my car I could feel the difference instantly (their website wasn't kidding!), I didn't have a thermometer to test but I'm sure it's gotten at least 10-15 degrees colder now, and it cools off much faster when I start my car so I don't have to wait as long to cool off when it's been sitting in a parking lot all day. Here is their website if you want to take a look: - I can attest it works great.

    I see the car is Toyota. I have recharged my Toyota 2 times. The gauge on the second fill kit was averaged for most North American built cars. I got some pressure info off the Net for my car. Turned out I had to over charge my system according to the gauge in order to have the pressure needed for ice cold air. It does take some time too get there too. Also do not forget to roll back the puncture pin. At first this last time I had not turned it out enough after puncturing the can to get the pressure i needed. Cheers, Phil

    Please be careful refilling freon. I put too much in my system and it shut itself down. Once removed the system resumed properly. Jet be careful

    Great how to, As an Automotive Tech I need to make clear a few additional items. I really appreciate the note about not using sealers and snake oil. The author is correct that it will create more damage than good. Additionally with modern reclaiming and recycling equipment the repair shop my turn you down once they run the refrigerant id machine on the system. As refrigeration equipment is expensive we (they) do not want sealant or the like inside the reclaiming/recycling tanks. Also modern refrigeration systems hold small amounts of refrigerant compared to old R-12 systems from yester-year. For example a late model Honda civic may hold only 14oz. which is less than a pound. A 1973 chevy impala may have held 4.5 pounds of refrigerant. There are a/c systems that hold only 9 oz. so it would be very easy to overcharge they system. Late model cars are equiped with many sensors and pressure switchs that can shut off your compressor and prevent compressor engagement. I can not tell you how many overcharged systems I have serviced that had electrical problems or the electric cooling fan(s) not working. Please make sure one does a complete inspection prior to adding refrigerant to avoid costly repairs.

    COOL instructable... I am also happy to see no one has attacked this as far as evil refrigerant use. So this is the same stuff that is used in modern refrigerators as well, yes?

    The freon/refrigerant you add at the fill port goes down that hose directly into the compressor. The refrigerant is in a gaseous state inside this line. If you turn the can upside down, it will dispense liquid refrigerant instead of gaseous. Since liquid is incompressible, it will break the compressor when it hits it.

    When the can is empty, no liquid will come out when you turn it upside down, or it will vaporize very quickly inside the line. The reason for turning it upside down is to drain out any additives or oil that may be in the can to lubricate your A/C system that did not vaporize.

    Great 'ible! I am so doing this. Under filling the system you are very adamant about not turning the can upside down, but its the first step under changing the can. Can explain why it is not to safe (assuming based on CAPS) to turn the can upside, but OK to do so when the can is empty? Is this a precaution to avoid 'Simon Phoenix'ing' oneself or does it affect the pressure going into the system?