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 air temperature is within 15 - 35 °C (59 - 95 °F).
- Relative humidity is within 30 - 70%.
- There is no wind indoors.
- HVAC unit is normal condition.
- There is no air leakage from air ducts.
- Condenser fins are clean.
- Air filter is not clogged with dirt and dust.
- Battery voltage is 12 V or more.
- Radiator cooling fan operates normally.
2) Make sure that high pressure valve (1) and low pressure valve (2) of manifold gauge (3) are firmly closed.
3) Connect high pressure charging hose (4) to high pressure service valve (5) on vehicle, and connect low pressure charging hose (6) to low pressure service valve (7) on vehicle.
4) Bleed the air in charging hoses by loosening their respective nuts on manifold gauge, utilizing the refrigerant pressure. When a hiss is heard, immediately tighten nut.





5) Warm up engine to normal operating temperature (engine coolant temperature at 80 - 90 °C (176 - 194 °F)) and keep it at specified idle speed.
6) Operate A/C at the following conditions.
- A/C switch at ON position
- Blower speed selector at max position
- Air flow selector at "VENT" position
- Temperature selector at max cool position
- Vehicle door at all open
- Air inlet door at recirculation position
7) Wait for ten minutes to stabilize A/C operation.

8) Keep all windows, doors and engine food open.
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 (3) 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 table.

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






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









High pressure gauge

Symptom Related Diagnostic Procedures





Low pressure gauge





11) Check inlet port temperature-to-outlet port temperature relationship using graph.

For example, if A/C evaporator inlet port temperature is 30 °C (86 °F) and center ventilation louver temperature is 14 °C (57.2 °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 duct





NOTE:
If ambient temperature is approximately 30 °C (86 °F), it is possible to diagnose A/C system in detail referring to the following table.