How Do You Do a Car AC Recharge?

Your car's AC system is a closed loop that relies on a cycle of condensation and evaporation of a refrigerant to provide cooling —exactly like your refrigerator or home AC. Your refrigerator, however, doesn't have to operate with the extreme temperatures and vibration under the hood of a vehicle.

The seals, O-rings and hoses on a car AC are slightly porous and tend to seep out refrigerant. Even a late-model vehicle can lose 5 to 10 percent of its refrigerant in the off season. Running the AC with low refrigerant levels isn't a good idea, especially since refrigerant contains an oil that lubricates the compressor's piston and other moving parts. Performing a car AC recharge isn't a complicated task, though—and you can save yourself some time and expense by learning how to do it yourself. Here's how.

Materials Needed:

Tip No .1: Some refrigerant canisters require their valve and hoses to be "tapped" into the can and don't include gauges. Go for the style with trigger, gauges, and hose, complete and ready to use.

Tip No. 2: It's important to remember the insulated gloves and safety goggles. Refrigerant is cold enough to cause immediate frostbite if it gets on exposed skin.

How to do a car AC recharge

  1. Start your engine and turn the AC to max. With the hood up, listen and determine whether the AC compressor clutch is engaging. It may cycle on and off with a metallic clicking if the refrigerant is low, or it may not engage at all.
  2. Locate the AC's low pressure port. The low pressure port will be on the accumulator, which is a cylinder-shaped assembly that's usually over by the passenger side fender well, with lines running to and from it. The low pressure port will have a plastic cap over it and is much like a Schrader valve that you'll find on a tire. The system's low and high pressure valves are two different sizes, making it fairly impossible to connect the car AC recharge kit improperly.
  3. Connect the refrigerant canister's hose to the low pressure port. The hose will have a spring-loaded collar-type fitting at the end; place this collar over the valve and press firmly until you hear it click into place.
  4. Begin charging. Invert the refrigerant canister and pull the trigger for 5 to 10 seconds at a time. Shake the canister and flip it right-side-up periodically, and continue to charge in 5- to 10-second bursts. Watch the gauges as the system recharges; you should recharge until the gauges reach 40 psi. This may take 20 to 30 minutes, and if your AC system is really low, you may need more than one 32 oz. can of refrigerant to fully recharge it.
  5. Check the AC temperature in the car. Place your thermometer in the AC vents and monitor the temperature. A fully charged system should be blowing air at 28 to 35 degrees.

Note: If you find yourself needing a car AC recharge more than once a season, chances are your system has a major leak of refrigerant somewhere. This type of leak needs to be repaired by a qualified professional.

Last updated February 16, 2019