How to Add R-134a Refrigerant

by Lee Sallings

Over time, the seals and connections in your vehicle's air conditioning system can allow a small amount of R-134a refrigerant to leak past and escape into the atmosphere. During cold weather in particular, the rubber seals shrink and provide a less secure seal. Adding R-134a refrigerant to replace the leaked refrigerant can be done at home by the average do-it-yourself mechanic for a fraction of the cost of paying an auto repair shop to perform the procedure.

Step 1

Attach the gauge set to the service ports located on the high-pressure and low-pressure aluminum a/c lines. These ports are found on the passenger side of the engine compartment in most cases. The blue hose of the gauge set is attached to the low-pressure port, and the red hose is attached to the high-pressure port. On vehicles equipped with R-134a refrigerant, these ports are a standard size and the hoses cannot be attached incorrectly.

Step 2

Set the controls of the a/c system, located in the vehicle's dash, to provide maximum a/c, medium blower speed and recirculating air. Start the engine and allow it to run while you add refrigerant and observe the gauges.

Step 3

Screw the can tap to the yellow hose on the gauge set and screw a can of refrigerant to the tap. Open the can using the thumbscrew on the tap. Open the blue low-pressure valve on the front of the gauge set to add refrigerant from the can.

Step 4

Monitor the gauge readings by closing the valve every 30 seconds to observe the pressures displayed on the gauges. The system is full when the low-pressure gauge reads 35 psi +/- 5 psi, and the high-pressure gauge reads 350 psi +/- 50 psi.

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