How to recharge car AC with R134A

R134a is the most popular refrigerant to charge the AC systems inside the car.
Keep in mind that you will need to vacuum the car if the AC is discharged completely.


• You need an AC main fold gauge and a vacuum pump.
• AC Main fold gauge has three lines : blue, red and yellow. Connect yellow to vacuum pump, red to large fitting and blue to small fitting in the car.

• Make sure that both blue and red are off. Start the vacuum. Once the vacuum is started, please crank the base near yellow line to remove any atmospheric pressure. After that ,open both the blue and red lines slowly.
• Keep the vacuum running for 30 minutes or till the reading shows less than zero on both the high pressure (red) and low pressure (blue).
• Now you have removed traces of old refrigerant, oils and dirt to the last.

Now recharge the Car air conditioner

• Loosen the cap on AC compressor. Attach the end of adapter (It will be coming out of r134a can).Remove the yellow line from vacuum and attach it to can. Keep the remaining setting from vacuum process mentioned above.
• Go and start the car and turn the AC to maximum.
• Close both the red and yellow lines.
• Now screw the top of r134a can. It will puncture the can and release the refrigerant. Just shake it and turn it upside down.
• Open both the high pressure and low pressure lines.
• The can will start to feel cold and light, Once the refrigerant starts to enter the ac system.
• Go inside the car and feel the AC. If it is cold then your ac is charged.
• Check the pressure gauges to make sure that you filled it to perfection. Generally it is 200 psig on high side and 30 psig on low side. But the better way is to match it with the specifications provided by your manufacturer.
• Remove the can and screw the cap back on compressor.

FAQ on Recharging the Car AC

How much R134A refrigerant should i add to my car ac system?

First thing is to check that your AC is fully discharged or not. If your AC is discharged completely then you have to vacuum it completely. Just run the vacuum pump for 30 minutes (approximately).Please check the service manual provided by car dealer or look at the sticker below the hood to find the amount of R134A needed to completely charge the system. For example if the required amount of refrigerant is 2 pounds than you have to charge it with 3 12 ounce cans of r134a refrigerant.

What to do, if the car ac is not discharged completely?

Find the specified pressure reading of both high pressure and low pressure from your service manual. Just connect the AC main fold gauges to your car. After that puncture the can to start the flow of R134A in the system. Keep an eye on the pressure shown in AC gauges. Once it reaches the specified pressure, remove the can.

Is it ok to mix R12 and R134A?

Never. Mixing R12 and R134A will create a pressure that will be higher than both R12 and R134A.This can damage your air conditioner system. It will create a black goo that will clog your car ac system resulting in black death syndrome. The minimum amount charged to clear the black death syndrome is one thousand dollars. It can also damage compressor and pressure relief valve.

Can I add R134A in R12 systems?

If you want to add R134A in your car model designed for r12 (prior to 1995),then you have to go to dealer and ask for proper retrofitting. There is no easy way out.

Precautions while filling R134A in system

• Keep your hands off the moving engine parts while fitting the can and gauges.
• Avoid direct skin contact with R134A.
• Fill the refrigerant as per the specifications. Too much R134A will blow the gaskets and too little will overwork the compressor.
• Never release refrigerant in air. It is illegal because it can deplete ozone layer.
• Always shake and turn the can upside down while filling refrigerant.
• Wear goggles and gloves for safety to protect your eyes and body in case of accidental explosion.

How to detect Leaks while filling R134A

Your engine has a leak problem if the pressure does not rises in the gauge even after adding one can of R134A.It is better to shut off engine to hear any leakage. It is good if you add green dye after evacuation process. It will help to find leaks easily.

How to find right refrigerant for my car

The year of car model is related to the choice of car ac refrigerant. Generally if the car model is of before 1995 than it will have R12 as refrigerant and models made after 1996 use R134A as preferred refrigerant .You can ask the dealer, check the service manuals or look at the sticker under the hood.

Top R134A Refrigerants

Rating (out of 5)
18 oz4.0$26.06
List Price: $32.99
12 packs of 12 oz4.8$58.34
List Price: $171.95
12 oz4.8$12.75
List Price: $21.99
30 lbs4.8$135.00

Can i use external heat source to make refrigerant transfer faster

No. External heat will increase the pressure and it may explode damaging you and your property. An easy way out is to take warm tap water and dip can into it from time to time and shaking it.

Any alternative refrigerant to R134A

Demand is growing for refrigerants with even lower warming potential than R134A.The popular refrigerants are R744 (CO2 based) and HFO-1234YF created by Honeywell and Dupont.

Time to empty a 12 ounce can of R134A Refrigerant

It will depend upon the difference of pressure between can and the system. You have to wait till the pressure on gauges match the specified pressure on Can. You can increase the rate of refrigerant transfer by dipping the can in warm water or shaking it or turning it upside down. An empty can will be cold and feel light.
Retrofit kits