Testing Air Conditioning Performance

Performance testing provides a measure of air conditioning system operating efficiency by measuring and comparing pressures at the high-pressure and low-pressure sides of the refrigeration system and the passenger compartment.

Before making the air conditioning performance test, a functional test should be made to assure that the air distribution system air valves are functioning properly to route all the air passing through the evaporator to the outlets.

Connect the high-pressure gage to the high-pressure side service fitting. Connect the low-pressure gage to the low-pressure side service fitting. Both gage valves must be closed while making the connections. The center hose fitting also must be closed, and must remain closed during the performance test.

The hood must be open and all doors and windows must be closed during the test. The air conditioning controls must be set for "MAX" air conditioning, "HI" blower speed and full "COOL" temperature.

Place a high volume fan in front of the radiator grille to insure an adequate supply of airflow across the condenser. After idling the engine for ten minutes, increase engine speed to 2000 RPM for the test.

Just before making the performance test, determine the temperature and relative humidity of the ambient air (air being blown against the condenser). Then measure the temperature of the air being discharged from a center instrument panel outlet. Read the low-pressure gage. Record and compare the readings to the data listed in Fig. Figure .

If operating pressures are within the normal range, the refrigeration system can be considered to be operating properly. This can be further confirmed by the outlet air temperature reading. Slight variations from the published readings can be considered acceptable if experience has shown that such minor deviations do not indicate a problem.