Heating and Air Conditioning: Testing and Inspection

1. Install manifold gauge set.
2. Run engine at 2000 RPM and set controls for maximum cooling and high blower speed.
3. Open all windows and doors.
4. Place dry-bulb thermometer in air outlet.
5. Place psychrometer (combination wet and dry-bulb thermometers) close to cooling unit inlet.
6. Ensure reading on high pressure gauge is 199-228 psi.
7. If reading is too high, pour water on condenser. If reading is too low, cover front of condenser.
8. Ensure reading of dry-bulb thermometer at air inlet is 77-95°F.

Fig. 1 Relative Humidity Graph:

9. Calculate relative humidity from psychrometric graph, Fig. 1, by comparing wet and dry bulb readings of psychrometer.
10. Measure dry-bulb temperature at cool air outlet, then calculate difference between inlet dry-bulb and outlet dry-bulb temperatures.

Fig. 2 Cooling Performance Chart:

11. If intersection of relative humidity and temperature difference is between two hatched lines, Fig. 2, cooling performance is satisfactory.

Fig. 4 Performance Test Diagnostic Chart (Part 1 Of 4):

Fig. 4 Performance Test Diagnostic Chart (Part 2 Of 4):

Fig. 4 Performance Test Diagnostic Chart (Part 3 Of 4):

Fig. 4 Performance Test Diagnostic Chart (Part 4 Of 4):

12. If system performance is not satisfactory, refer to Fig. 4. The marked portion of each gauge scale indicates a range based on the assumption that the air conditioning system is in good working order.