Disconnect the power to the walk-in cooler. Put on your safety goggles and gloves.
Go to the back of the walk-in cooler and look at the service tag. This should give you the name of the refrigerant needed to charge your unit.
Unscrew the middle hose fitting from the refrigeration manifold gauge. Connect the gauge to the service port on the unit. This is located next to the compressor.
Connect your refrigerant tank to the manifold gauge and then open the gauge's centerline. Close the centerline after a second. This will purge the line of any air. Connect the other end of the gauge to the service valve on the cooler.
Open the centerline of the gauge and allow the refrigerant to flow into the service valve. Wait for the needle on the gauge to go into the “Green” section. Turn the regulator to the “Off” position.
Disconnect the gauge from the unit and then replace the cap on the service port.