How to Put Coolant in Your AC Unit

Your car's air conditioning unit regulates temperature by using freon coolant in combination with the fans and vents of the system. Too much coolant inside the air conditioning unit will cause overflow in your system, which can rupture the pipes. On the other hand, too little coolant reduces the system's ability to effectively cool your car with anything beyond the vent fans. Fortunately, if your system is low on coolant it is a relatively simple procedure to fill it yourself.

Things You'll Need

  • Owners manual
  • Coolant
  • Crescent wrench
  • Car's keys
  • Coolant gauge
  • Vacuum pump
  • Turn your car to the on position without turning over the ignition and starting the car. This will allow you access to the accessories without having the engine actually running. Turn your fans to high and turn your air conditioning knob to the coldest setting.

  • Open your hood and use your owners manual to identify the low- and high-pressure lines for your AC unit. These will be shown on the diagram of your engine in your manual.

  • Unscrew the cap of your low-pressure line using the crescent wrench and screw the low-pressure hose from your air conditioning gauge on to the area where you just removed the cap. Your low pressure hose is the one to the left of the yellow hose on your air conditioning gauge. Make sure you screw your hose tight onto the cap to avoid any air leaks.

  • Screw the yellow hose from your gauge on to your vacuum pump. If your gauge reads anywhere from 0 to 25 you need to put more coolant into the system.

  • Hook your vacuum pump up to the yellow hose in the middle of your air conditioning gauge. Turn the pump on and leave it for about 45 minutes to an hour. This will remove moisture from the system, which can interfere with the new coolant.

  • Turn off your vacuum pump and unscrew the yellow middle hose from it. Screw the yellow hose on to your coolant container and use your crescent wrench to loosen the connection from the hose to the pump itself until it hisses. Then tighten it back up. This removes any excess air, which can slow down the coolant process and put unwanted oxygen in your coolant.

  • Open up your gauge by turning the handle on the left side of the gauge to the left. Wait until your gauge reads between 25 and 45 and tighten your gauge back up. You now have the correct amount of coolant inside your AC unit.