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A/C System Performance Inspection: Notes

WARNING: This page is about a different car, the 2008 Suzuki Grand Vitara. However, it is still accessible from the selected car via links, so may be relevant.
  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.
    • Are 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.
    WARNING: Make sure to connect high and low pressure charging hoses to correct valves.
    Connecting them in the other way around may cause charging hoses and refrigerant container to burst.
    Fig 1: Connecting High And Low Pressure Charging Hoses To Correct Valves
    G05472929Courtesy of SUZUKI OF AMERICA CORP.
  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.
    Fig 2: 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
    G05472930Courtesy of SUZUKI OF AMERICA CORP.
  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) 

    Pressure on high pressure gauge (HI): 1340 - 1670 kPa (13.4 - 16.7 kg/cm 2  , 191 - 237 psi) 

    Pressure on high pressure gauge (LO): 280 - 390 kPa (2.8 - 3.9 kg/cm 2  , 40 - 55 psi) 

    NOTE: Pressure registered on gauge varies with ambient temperature. Therefore, use the graphs when determining if pressures are normal or not.
    Fig 3: High And Low Pressure Gauge Temperature Graph
    G05472931Courtesy of SUZUKI OF AMERICA CORP.

    High pressure gauge 

    HIGH PRESSURE GAUGE REFERENCE

    Condition Possible Cause Correction
    Pressure is higher than acceptable range ("A" area) Refrigerant overcharged Recharge.
    Expansion valve frozen or clogged Check expansion valve.
    Clogged refrigerant passage of high side Clean or replace.
    Radiator cooling fan malfunction (Insufficient cooling of condenser) Check radiator cooling fan.
    Dirty or bent condenser fins (Insufficient cooling of condenser) Clean or repair.
    Compressor malfunction (Insufficient oil etc.) Check compressor.
    Engine overheat Check engine cooling system referring to ENGINE COOLING SYMPTOM DIAGNOSIS .
    Pressure is lower than acceptable range ("B" area) Insufficient refrigerant (Insufficient charge or leakage) Check for leakage, repair if necessary and recharge.
    Expansion valve malfunction (valve opens too wide) Check expansion valve.
    Compressor malfunction (Insufficient compression) Check compressor.

    Low pressure gauge 

    LOW PRESSURE GAUGE REFERENCE

    Condition Possible Cause Correction
    Pressure is higher than acceptable range ("C" area) Expansion valve malfunction (valve opens too wide) Check expansion valve.
    Compressor malfunction (Insufficient compression) Check compressor.
    Pressure is lower than acceptable range ("D" area) Insufficient refrigerant (Insufficient charge or leakage) Check for leakage, repair if necessary and recharge.
    Expansion valve malfunction (valve opens too narrow) Check expansion valve.
    Clogged refrigerant passage (crashed pipe) Repair or replace.
  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 16°C (60.8°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.
    Fig 4: Air Inlet And Air Outlet Port Temperature Graph
    G05472932Courtesy of SUZUKI OF AMERICA CORP.
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