A/C System Performance Inspection

A/C System Performance Inspection

1) Confirm that vehicle and environmental conditions are as follows.
- Vehicle is put indoors.
- Ambient temperature is within 25 - 35 °C (77 - 95 °F).
- Relative humidity is within 30 - 70%.
- There is no wind indoors.
- HVAC unit is normal.
- Blower motor is normal.
- There is no air leakage from air ducts.
- Condenser fins are clean.
- HVAC air filter is not clogged with dirt and dust (if equipped).
- Battery voltage is about 12 V.
- Radiator cooling fan operates normally.
2) Make sure that high pressure valve (1) and low pressure valve (2) of manifold gauge are firmly closed.
3) Connect high pressure charging hose (3) to high pressure service valve (5) on vehicle and low pressure charging hose (4) to low pressure service valve (6).
4) Bleed the air in charging hoses (3) and (4) by loosening their nuts respectively utilizing the refrigerant pressure. When a hissing sound is heard, immediately tighten nut.






5) Warm up engine to the normal operating temperature and keep it at the specified idle speed.
6) Turn A/C switch ON, set blower speed selector at maximum speed position, temperature selector at maximum cold position, air flow selector at face position, and air intake switch at recirculation position. (Confirm that A/C compressor, A/C condenser cooling fan and radiator cooling fan are working.)
7) Wait for ten minutes to stabilize the A/C operation.
8) Open all door windows, front doors and engine hood.
9) With about 20 mm (0.8 in.) of dry bulb thermometer (1) put right in front of center ventilation louver and a wet and dry bulb thermometer (2) near air inlet of HVAC unit.






10) Check for each pressure of low side and high side if it is within shaded range of graph. If each gauge reading is out of specified pressure, correct defective part referring to the following table.

When diagnosing troubles of abnormal pressure on the low side and high side for each pressure more specifically, refer to Trouble Diagnosis for Abnormal Pressure Trouble Diagnosis for Abnormal Pressure:Manual A/C.

NOTE:
Pressure registered on gauge varies with ambient temperature. Therefore, use the graphs when determining if pressures are normal or not.

Low side and high side pressure example, Gauges should read as follows when ambient temperature is 30 °C (86 °F)














High pressure gauge







Low pressure gauge





11) Check inlet port temperature-to-outlet port temperature relationship using the graph. For example, if temperature near air inlet of HVAC unit is 30 °C (86 °F) and the one at air outlet of center ventilation louver is 17 °C (62.6 °F), their crossing point is within acceptable range as shown in the graph. In this case, cooling performance is satisfactory and proper.
12) If crossing point is out of acceptable range, diagnose trouble referring to the following table.











Thermometer at center ventilation louver