How to Add Refrigerant to an Auto A/C

For cars manufactured before 1995, there's really no need to learn how to add refrigerant to the A/C unit. That's because cars manufactured prior to that use R12 refrigerant which is now only available to an authorized repair shop where a technician can do the work. R12 is still available to them for repairs as recycled R12 refrigerant. The good news is that the air conditioning in cars manufactured after the 1994 model year can still be recharged by their owners.

Instructions

1

Connect the service hose and low pressure gauge that are included in an A/C recharging kit to a can of 134a refrigerant following the instructions that come with the A/C recharging kit. Turn the pin valve on the service hose clockwise by hand until it punctures the top of the can.

2

Unscrew the cap from the vehicle's low-pressure side A/C service fitting by turning it counterclockwise by hand. The location of the valve will vary from vehicle to vehicle. Refer to the vehicle manufacturer's shop service manual for information on where to find the valve.

3

Purge air out of the service house by slowly opening the pin valve, turning it counterclockwise by hand, allowing some of the refrigerant to escape. Close the valve, turning it clockwise, and immediately connect the service hose to the A/C system by retracting the sleeve on the quick coupler of the service hose and inserting the hose onto the low-pressure fitting and releasing the sleeve of the quick coupler.

4

Start the engine and set the air-conditioning controls in the vehicle to maximum.

5

Reopen the pin valve completely; ensuring the can is in an upright position so that only vapor is sucked into the AC system.

6

Observe the reading of the low-pressure gauge. When the gauge reads between 25 and 40 psi, close the pin valve on the A/C recharging hose. If a second can of refrigerant is required, it can be added by first closing the pin valve on the recharging hose, detaching the empty can from the hose and installing a fresh can on the hose following the directions provided with the recharging kit. Open the new can as before and keep it open until the pressure gauge on the low side reads between 25 and 40 psi. The system is fully recharged at this point.

7

Close the pin valve and disconnect the service hose from the low-side service valve. Replace the cap on the low side service fitting.