Refrigerant Pressure Check

Install the manifold gauge. (See REFRIGERANT SYSTEM GENERAL PROCEDURES .)
Start the engine and after it is warmed up, run it at a constant 1,500 RPM.
Set the fan speed MAX HI.
Turn the A/C switch on.
Set to RECIRCULATE mode.
Set the temperature control to MAX COLD.
Set to VENT mode.
Close all the doors and all the windows.
Measure the ambient temperature and high- and low-pressure side reading of the manifold gauge.
Verify that the intersection of the pressure reading of the manifold gauge and ambient temperature is in the shaded zone.

If there is any malfunction, inspect the refrigerant system according to the troubleshooting chart.

Fig 1: Ambient Temperature Pressure Graph

Courtesy of MAZDA MOTORS CORP.