How do I use an R-134a AC Recharge Kit?

Alright ladies and gentlemen. So it is summer and it’s a damn hot day and your car’s air conditioner is blowing warm air. You went on over to the auto-parts store or on and purchased yourself a R-134a air conditioner recharge kit. Now that you have the kit in hand the question is how do you use it? Well folks let’s dive in and take a look:

What You’ll Need

  • Your car, obviously!
  • Safety glasses and gloves – You don’t want any refrigerant burns, trust me!
  • A thermometer showing outside temperature.
  • A R-134a AC recharge kit. (We prefer the AC Pro from

How To Use a AC Recharge Kit in 10 Steps!

  1. Safety First – Be sure to put on safety eye glasses and mechanic’s gloves. Always watch your surroundings and ensure that you are as safe as possible.
  2. Before we can use the 134a AC recharge kit you will need to unscrew the hose/gauge from the top of the can, pull off the seal, and then tightly screw back on the hose and gauge to the can.
  3. Before we do anything we first need to identify where the low-side service port is on your vehicle’s air conditioning system. The low-side service port will always be on the larger sized aluminum tubing between the AC’s compressor and your car’s firewall. An example picture of a low-side service port is to the right, just remember that each car is different. Heck, each model year is different. To assist with this some cars have an ‘H’ on high pressure side and a ‘L’ on the low pressure port. Before doing anything please ensure that you are using the right port. If you are having trouble finding this port it is best to look up your car’s layout either online or in the instruction manual. Low Side Service Port
  4. Once we have identified the service port we can now start the engine of your vehicle and turn on the air conditioner. Ensure that the air conditioner is powered on to maximum cool and maximum blowing capacity.
  5. With the vehicle on then connect the coupler on your recharge kit to the low side service port that we identified in the first step. The coupler should snap and lock into place. (You may need to pull back the collar to connect the coupler.)
    1. If you find that the coupler is not fitting onto your low side service port then stop! This could be a few things. The first and most likely is that you are trying to put it on the high pressure port instead of the low pressure. A secondary scenario could be you have a newer car model you may in fact be using the new 1234yf refrigerant. If this is the case then you will need to visit a dealership as there are not recharge kits out there yet for 1234yf.
  6. Once this is done you can now check the pressure gauge. (A/C recharge kits come with a built-in pressure gauge.) Please note that it is critical that your compressor be running in order to check the pressure. You should be able to see the pulley of the compressor spinning if it is working correctly. If your compressor is not coming on then either there is no refrigerant left in your system or the compressor may be faulty. In this instance you may need to contact a mechanic.
  7. Depending on the gauge you will either need to wait for the appropriate ambient temperature or set the gauge accordingly to the ambient temperature. If the pressure gauge is below the ambient air temperature and the compressor is running then you can now begin to charge the AC system.
    1. Please note that if the gauge is in the red zone then that may mean that your compressor is not on and that your system is completely out of refrigerant. In this instance you can attempt to fill up your system with cans of 134a but it may be best to have a mechanic review the system as your compressor may be faulty.
  8. Before you begin charging the system shake the cylinder very well. You can now begin squeezing the trigger to begin charging the system. While charging be sure to hold the can up right alternating between the twelve and three o’clock positions frequently.
  9. It is important to watch your gauge when charging. You do not want to overcharge your system as you will risk part failure. When the pressure gauge has reached the ambient temperature your system will be charged.
  10. After charging remove the coupler and refasten the service cap. Store the remaining recharge kit in a moisture free and climate friendly environment for future use. Also be sure to keep the hose and gauge tightly sealed against the can of refrigerant to ensure no leaks occur.


After charging your system you should now feel the cold air blowing in your cabin. If you do not experience cold air or if the cold air does not last for an extended period of time then that means that you may have a large leak in your air conditioning system, your compressor is faulty, or a host of other problems. In these instances you will need to diagnose where the problem area, replace the appropriate parts, and then recharge your system. These steps are best done by a professional.

Lastly, if you haven’t bought your 134a AC recharge kit yet please check out some of the top brands below from partner: