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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.
    Fig 1: Inspecting Peformance Of A/C System
    G08894512Courtesy 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: Putting Bulb Thermometer In Front Of Center Ventilation Louver
    G08894513Courtesy 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) 1400 - 1595 kPa (14.3 - 16.3 kg/cm2 , 203 - 231 psi)
    Pressure on low pressure gauge (LO) 260 - 374 kPa (2.7 - 3.8 kg/cm2 , 37.7 - 54.2 psi)
    NOTE: Pressure registered on gauge varies with ambient temperature. Therefore, use the graphs when determining if pressures are normal or not.
    Fig 3: Low Side And High Sides Pressure Graph
    G08894514Courtesy of SUZUKI OF AMERICA CORP.
    HIGH PRESSURE GAUGE

    Condition Possible Cause Correction
    Pressure is higher than acceptable range ("H" 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 System Symptom Diagnosis  .
    Pressure is lower than acceptable range ("I" 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

    Condition Possible Cause Correction
    Pressure is higher than acceptable range ("J" area) Expansion valve malfunction (valve opens too wide) Check expansion valve.
    Compressor malfunction (Insufficient compression) Check compressor.
    Pressure is lower than acceptable range ("K" 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 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.
    Fig 4: Inlet Port Temperature-To-Outlet Port Temperature Relationship Graph
    G08894515Courtesy of SUZUKI OF AMERICA CORP.
THERMOMETER AT CENTER DUCT

Condition Possible Cause Correction
Crossing point is higher than acceptable range ("H" area) Insufficient or excessive charge of refrigerant Check refrigerant pressure.
Dirty or bent A/C evaporator fins Clean or repair.
Air leakage from cooling (heater) unit or air duct Repair or replace.
Malfunctioning, switch over function of damper in cooling (heater) unit Repair or replace.
Compressor malfunction Check compressor.
Crossing point is lower than acceptable range ("I" area) Insufficient air volume from center duct (Heater blower malfunction) Check blower motor and fan.
Compressor malfunction Check compressor.
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.
Condition Possible Cause Correction
Manifold Gauge MPa (kg/cm2 ) (psi) Detail
Lo Hi
0.26 - 0.37 (2.7 - 3.8) (37.7 - 54.2) 1.40 - 1.60 (14.3 - 16.3) (203 - 231) Normal condition - -
Negative pressure 0.5 - 0.6 (5 - 6) (71.2 - 85.3) The low pressure side reads a negative pressure, and the high pressure side reads an extremely low pressure. Presence of frost around tubing to and from receiver/dryer and expansion valve. Dust particles or water droplets are either stuck or frozen inside expansion valve, preventing the refrigerant from flowing. Clean expansion valve. Replace it if it cannot be cleaned. Replace desiccant. Evacuate the A/C system and recharge with fresh refrigerant.
Normal: 0.26 - 0.37 (2.7 - 3.8) (37.7 - 54.2)
↑ ↓
Abnormal: Negative pressure		 Normal: 1.40 - 1.60 (14.3 - 16.3) (203 - 231)
↑ ↓
Abnormal: 0.7 - 1.0 (7 - 10) (100 - 142)		 During A/C operation, the low pressure side sometimes indicates negative pressure, and sometimes normal pressure. Also high pressure side reading fluctuates between the abnormal and normal pressure. Expansion valve is frozen due to moisture in the system, and temporarily shuts off the refrigeration cycle. Replace expansion valve.
Replace desiccant. Evacuate A/C system and recharge with fresh refrigerant.
0.05 - 0.15 (0.5 - 1.5) (4.2 - 21.3) 0.7 - 1.0 (7 - 10) (100 - 142) Both low and high pressure sides indicate low readings. Output air is slightly cold. Insufficient refrigerant in system. (Refrigerant leaking) Using a gas leak detector, check for leaks and repair as necessary.
Recharge with specified amount of refrigerant.
If the pressure reading is almost 0 when the manifold gauges are attached, check for any leaks, repair them, and evacuate the system.
0.4 - 0.6 (4 - 6) (56.9 - 85.3) Pressure on low pressure side is high. Pressure on high pressure side is low. Both pressure becoming equal right after A/C is turned OFF. Internal leak in compressor Inspect compressor and repair or replace as necessary.
0.35 - 0.45 (3.5 - 4.5) (50 - 64) 2.0 - 2.5 (20 - 25) (285 - 355) High pressure reading on both low and high pressure sides. Overcharged A/C system.
Faulty condenser cooling operation. Faulty radiator fan operation.		 Adjust refrigerant to specified amount.
Clean condenser. Inspect and repair radiator fan.
High pressure reading on both low and high pressure sides. Low pressure side tubing is not cold when touched. Presence of air in A/C system. (Improperly evacuated) Replace desiccant. Inspect quantity of compressor oil and presence of contaminants in oil. Evacuate system and recharge with fresh refrigerant.
0.45 - 0.55 (4.5 - 5.5) (64 - 78) High pressure reading on both low and high pressure sides. Large amount of frost or dew on the low pressure side tubing. Faulty expansion valve.
Refrigerant flow is not regulated properly.		 Replace expansion valve.
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