Refrigerant Pressure Check

Connect the manifold gauge.
Start the engine and after it is warmed up, run it at a constant 1,500 rpm.
Set the fan switch to 4th speed.
Turn the A/C switch on.
Set to RECIRCULATE mode.
Set the temperature control to MAX COLD.
Set the VENT mode.
Close all the doors and all the windows.
Measure the manifold gauge reading and ambient temperature.
Verify that the high and low pressure readings are within each shaded zone.
- If there is any malfunction, inspect the refrigerant system according to the troubleshooting chart.
  
  Fig 1: Verifying Pressure Characteristics
  Courtesy of MAZDA MOTORS CORP.