How to Recharge Your Vehicle's Air Conditioning

When an air conditioning system loses its ability to cool properly, it may be necessary to recharge the system with new refrigerant. Keep reading for a R-134a A/C pressure chart and steps on how to recharge the A/C system when the system is low on pressure or has been vacuumed out following a repair.

Note: Always wear safety glasses and gloves when charging the A/C system.

Recharge Your AC in 8 Easy Steps

AC Temperature Pressure Chart for R-134a Recharging

Determine Ambient Air Temperature

If the temperature of the air is 55°F or below, do not charge the vehicle. It is recommended to use a charging hose with a gauge. The refrigerant packaging should contain a chart like the one above for determining what pressure to charge the system depending on the ambient air temperature. If no chart is provided, use the A/C pressure chart above this paragraph. Following the chart when recharging the system will ensure the system will operate efficiently.


Locate the Low-Side Service Port

This port is typically found on the line connecting the accumulator and compressor. The high side fitting is located between the AC compressor and condenser. Consult the service manual to verify the exact location of the low-side service port.

*Most 1994 and older vehicles used R12 as the original refrigerant, if the vehicle being serviced is still using R12, it must be evacuated and retrofitted. Mixing R12 and any other refrigerant is illegal. Never use the high-side port to add refrigerant, doing so is very dangerous and could cause harm.


Wipe Away Dust

Wipe away any dust with a clean rag and then remove the cap from low-side service port.


Attach the Charging Hose

Attach the charging hose to the low-side service port and ensure that you have a secure connection. If the hose does not attach easily you may be using the wrong port.


Add Refrigerant

Following the instructions on the refrigerant package, add refrigerant to the system.


Charge the System

After determining the correct pressures using the ambient air pressure chart, monitor the pressure readings constantly while charging the system.


Remove the Charging Hose

After the air conditioning system is charged to the proper pressure, remove the charging hose from the low-side service port, leaving the can attached to the charge hose, and store any additional refrigerant in a dry, cool spot.


Check the Service Port Cap Seal Before Reinstalling

Ensure that the seal beneath the cap does not have any cracks, nicks, or tears. This seal can be added protection if the Schrader valve ever formed a leak.

After you’ve recharged your air conditioning, the difference should be noticeable immediately. It may be worth checking the pressure once or twice after recharging in case the low refrigerant level was caused by a leak in the system. If you believe there is a leak, get a UV light and some UV dye so you can find the leak. The UV dye will make the hole visible when the UV light is shined onto the A/C components.

Whatever you need to work on your auto air conditioning system, you can get it at AutoZone.

Find a Nearby AutoZone Store

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Be sure to consult your owner’s manual, a repair guide, an AutoZoner at a store near you, or a licensed, professional mechanic for vehicle-specific repair information. Refer to the service manual for specific diagnostic, repair and tool information for your particular vehicle. Always chock your wheels prior to lifting a vehicle. Always disconnect the negative battery cable before servicing an electrical application on the vehicle to protect its electrical circuits in the event that a wire is accidentally pierced or grounded. Use caution when working with automotive batteries. Sulfuric acid is caustic and can burn clothing and skin or cause blindness. Always wear gloves and safety glasses and other personal protection equipment, and work in a well-ventilated area. Should electrolyte get on your body or clothing, neutralize it immediately with a solution of baking soda and water. Do not wear ties or loose clothing when working on your vehicle.

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