2. Start the engine and leave it running at 2000 rpm, set the temperature switch to the position corresponding to the maximum cooled air supply to the passenger compartment, and the fan switch to the position corresponding to the maximum speed.
3. Open all windows and doors.
4. Place the dry bulb probe into the cool air supply nozzle.
5. Place the psychrometer at the air intake point in the refrigeration circuit of the air conditioner.
6. Check the readings of the high pressure gauge, which should be in the range of 1.373-1.575 kPa. If the reading exceeds the upper limit indicated, pour water over the condenser. If the reading is below the lower limit, cover the front of the condenser.
7. Check dry bulb readings, which should be between 25-35°C.
8. Determine the relative humidity of the air according to the psychrometric graph by comparing the wet-bulb and dry-bulb temperatures of the psychrometer placed at the air intake of the air conditioner.
9. Determine the temperature using a dry bulb thermometer placed in the cooled air supply nozzle to the passenger compartment and calculate the difference between the dry bulb temperature at the air intake and the dry bulb temperature at the air outlet to the passenger compartment.
10. Verify that the intersection point of the relative humidity and temperature difference lines is within the black shaded area, indicating that the cooling capacity performance is within specification.