A/C System Performance Inspection - HVAC Manual
A/C System Performance Inspection1. Confirm that vehicle and environmental conditions are as follows.
- Vehicle is not exposed to direct sunshine.
- Ambient temperature is within 15 - 35 °C (59 - 95 °F).
- Air filter is not clogged with dirt and dust.
- Battery voltage is more than 12 V.
- Air intake actuator, temperature control actuator, and air flow control actuator are installed correctly. And, the actuators operate normally.
2. Make sure that high pressure valve (1) and low pressure valve (2) of manifold gauge set (3) are firmly closed.
3. Connect high pressure charging hose (4) to high pressure service valve (5) and connect low pressure charging hose (6) to low pressure service valve (7).
4. Bleed the air in charging hoses (4) and (6) by loosening their respective nuts on manifold gauge set (3), utilizing the refrigerant pressure. When a hissing sound 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. (Radiator cooling fan should not be working when checking temperature.)
6. Set A/C switch to ON position, blower speed selector at maximum speed position, temperature selector at maximum cool position, air flow selector at vent position and air intake selector at recirculation air mode. (Confirm that A/C compressor and condenser cooling fan are working. Keep all windows, doors and engine food open.
Performance diagnosis condition
- Ambient temperature: 15 - 35 °C (59 - 95 °F)
- Engine rpm: Keep to 1,500 rpm.
- Blower speed selector: Maximum speed position
- Temperature selector: Maximum cool position
- Air flow selector: Vent position
- Vehicle doors: All open
- Air intake selector: Recirculation air mode
7. With dry bulb thermometer (1) inserted into center ventilation louver and another one set near recirculation air inlet, read temperature difference.
8. 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.
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)
Pressure on high pressure gauge: 1400 - 1750 kPa (14.0 - 17.5 kg/sq.cm, 199.1 - 248.9 psi)
Pressure on low pressure gauge: 230 - 350 kPa (2.3 - 3.5 kg/sq.cm, 32.7 - 49.8 psi)
High pressure gauge
Low pressure gauge
9. Check for crossing point of center ventilation louver air temperature and recirculation air inlet temperature if it is within shaded range of graph. For example, if inlet temperature is 25 °C (77 °F) and center ventilation louver temperature is 8 °C (46 °F), their crossing point is within acceptable range as shown in graph. If crossing point is out of acceptable range, diagnose trouble referring to the given table.
Crossing point of center ventilation louver temperature and recirculation air inlet temperature