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Performance Test

CAUTION:
  • Air conditioning refrigerant or lubricant vapor can irritate your eyes, nose, or throat.
  • Be careful when connecting service equipment.
  • Do not breathe refrigerant or vapor.

The performance test will help determine if the A/C system is operating within specifications.

NOTE:
  • If accidental system discharge occurs, ventilate the work area before resuming service.
  • Additional health and safety information may be obtained from the refrigerant and lubricant manufacturers.
  1. Do the A/C system inspection (see A/C SYSTEM INSPECTION  ), and correct any problems found.
  2. Connect an R-134a refrigerant recovery/recycling/charging station to the high-pressure service port and the low-pressure service port, following the equipment manufacturer's instructions.
  3. Determine the relative humidity and air temperature.
  4. Open the glove box. Remove the glove box stop on each side, then let the glove box hang down (see GLOVE BOX REMOVAL/INSTALLATION ).
  5. Insert a thermometer (A) in the center vent.
    Fig 1: Inserting Thermometer In Center Vent
    G06680568Courtesy of AMERICAN HONDA MOTOR CO., INC.
  6. Place a thermometer (B) near the blower unit's recirculation inlet duct.
  7. Test conditions:
    • Move the vehicle out of direct sunlight and let it cool down to the surrounding (ambient) temperature. If necessary, wash the vehicle to cool it down more quickly.
    • The ambient temperature must be at least 60°F (16°C).
    • Open the hood.
    • Open the front doors.
    • Set the temperature control dial to Max Cool, the mode control switch to Vent, and the recirculation control switch to Recirculate.
    • Turn the A/C switch ON and the fan switch to Max.
    • Hold the engine speed at 1,500 rpm.
    • No driver or passenger's in the vehicle.
  8. Inspect the A/C components for the following conditions:
    • A/C compressor clutch not engaged
    • Abnormal frost areas
    • Unusual noises

      If you observe any of these conditions, refer to the SYMPTOM TROUBLESHOOTING .

  9. After running the air conditioning for 10 minutes under the above test conditions, read the delivery temperature from the thermometer in the center vent, the intake temperature near the blower unit, and the discharge (high) and suction (low) pressures on the A/C gauges.
  10. To complete the vent (delivery)/ambient air (intake) temperature chart:
    • Mark the vent (delivery) temperature on the vertical line.
    • Mark the ambient air (intake) temperature on the bottom line.
    • Draw a vertical line from the ambient air (intake) temperature mark.
    • Draw a horizontal line from the vent (delivery) temperature mark until it intersects the vertical line.
      NOTE: The vent temperature and the ambient air temperature should intersect in the shaded area. Any measurements outside the line may indicate the need for further inspection.
      Fig 2: Ambient Air (Intake) Temperature Vs. Vent (Delivery) Temperature Graph
      G06680569Courtesy of AMERICAN HONDA MOTOR CO., INC.
  11. To complete the high side (discharge) pressure/ambient air (intake) temperature chart:
    • Mark the high side (discharge) pressure temperature on the vertical line.
    • Mark the ambient air (intake) temperature on the bottom line.
    • Draw a vertical line from the ambient air (intake) temperature mark.
    • Draw a horizontal line from the high side (discharge) pressure mark until it intersects the vertical line.
      NOTE: The high side pressure and the ambient air temperature should intersect in the shaded area. Any measurements outside the line may indicate the need for further inspection.
      Fig 3: Ambient Air (Intake) Temperature Vs. High Side (Discharge) Temperature Graph
      G06680570Courtesy of AMERICAN HONDA MOTOR CO., INC.
  12. To complete the low side (suction) pressure/ambient air (intake) temperature chart:
    • Mark the low side (suction) pressure temperature along the vertical line.
    • Mark the ambient air (intake) temperature along the bottom line.
    • Draw a vertical line from the ambient air (intake) temperature mark.
    • Draw a horizontal line from the low side (suction) pressure mark until it intersects the vertical line.
      NOTE: The low side pressure and the ambient air temperature should intersect in the shaded area. Any measurements outside the line may indicate the need for further inspection.
      Fig 4: Ambient Air (Intake) Temperature Vs. Low Side (Suction) Temperature Graph
      G06680571Courtesy of AMERICAN HONDA MOTOR CO., INC.
PRESSURE TEST REFERENCE

Test results Related symptoms Probable cause Remedy
Suction and discharge pressures are normal Warm air from the vents.
  • The A/C system contains too much refrigerant oil
  • The air mix door is not operating properly
Suction and discharge pressures are roughly equal and steady The suction and discharge pressures equalize when the engine is revved. The A/C compressor clutch or the drive belt is slipping, or the A/C compressor shaft seal is leaking
  • Check whether the A/C compressor clutch or the drive belt is slipping.
  • If the drive belt is slipping, replace the drive belt (see ). If the A/C compressor clutch is slipping, replace it (see A/C COMPRESSOR CLUTCH OVERHAUL  ).
  • Check the A/C compressor shaft seal. If it's leaking, replace the A/C compressor (see A/C COMPRESSOR REPLACEMENT  ).
Suction and discharge pressures are roughly equal but fluctuate Suction and discharge pressures fluctuate while running. Pressures equalize as soon as the A/C compressor disengages. The A/C compressor discharge valve or the A/C compressor gasket is faulty Replace the A/C compressor (see A/C COMPRESSOR REPLACEMENT  )
Suction and discharge pressures are roughly equal and abnormally low The suction and discharge pressures do not change during continued operation. The A/C system is undercharged Recover refrigerant (see REFRIGERANT RECOVERY  ), then do the refrigerant leak check (see REFRIGERANT LEAK CHECK  ). Repair any leaks, then recharge the system (see SYSTEM CHARGING  ).
Suction and discharge pressures are abnormally high, but normalize when the A/C condenser is cooled The suction pressure decreases when cool water is sprayed on the A/C condenser. The A/C system is overcharged Recover refrigerant (see REFRIGERANT RECOVERY  ), evacuate the system (see REFRIGERANT RECOVERY  ), and recharge the system to specifications (see SYSTEM CHARGING  ).
Suction and discharge pressures are abnormally high, and refrigerant line temperatures are abnormal
  • The high pressure vapor line to the A/C condenser is too hot.
  • The low pressure liquid line from the expansion valve is not cold.
  • There is an abrupt temperature drop along a refrigerant line, or in the A/C condenser or evaporator.
 The A/C system refrigerant flow is restricted Replace the restricted line or component.
Suction and discharge pressures are abnormally high, but drop rapidly when the A/C compressor disengages
  • After stopping the A/C compressor, the discharge pressure quickly drops about 196 kPa (28 psi), then falls gradually.
  • The input and output temperatures at the expansion valve are not similar.
 There is excess air in the A/C system Recover refrigerant (see REFRIGERANT RECOVERY  ), evacuate the system (see REFRIGERANT RECOVERY  ), and recharge the system (see SYSTEM CHARGING  ).
Suction and discharge pressures are abnormally high, and there is little or no airflow through the A/C condenser Suction and discharge pressures normalize when water is splayed on the A/C condenser
  • The A/C condenser and/or radiator fins are clogged
  • The A/C condenser fins are damaged
  • The A/C condenser and/or radiator fans are not working properly
  • Clean debris from the A/C condenser and/or radiator fins.
  • Comb the A/C condenser fins to repair any damage.
  • Troubleshoot the A/C condenser fan and/or the radiator fan circuit(s).
The suction pressure is high and the discharge pressure is low. Both pressures are steady
  • The liquid line temperature is similar on both sides of expansion valve.
  • System pressures do not vary at a steady engine speed.
 The expansion valve is stuck open Replace the expansion valve (see A/C COMPRESSOR REPLACEMENT  ).
The suction pressure is low, the discharge pressure is high, and the refrigerant temperature changes abnormally somewhere in the system
  • The high pressure liquid line going into the expansion valve is cold.
  • There is an abrupt temperature drop in the line between the A/C compressor and the A/C condenser, or in the line between the A/C condenser and the expansion valve.
 The A/C system refrigerant flow is restricted Replace the restricted line or component.
The suction pressure is high, the discharge pressure is low, and there are particle contaminants in the refrigerant lines The expansion valve and/or the A/C compressor discharge hose are contaminated with metal flakes or desiccant particles. The A/C compressor is malfunctioning Replace the A/C compressor (see A/C COMPRESSOR REPLACEMENT  ). If the system is contaminated with desiccant, replace the receiver/dryer (see RECEIVER/DRYER DESICCANT REPLACEMENT  ).
The suction pressure is high, the discharge pressure is low, and the pressures quickly change when the A/C disengages The discharge and suction pressures equalize soon after the A/C compressor stops. The A/C compressor seal is faulty Replace the A/C compressor (see A/C COMPRESSOR REPLACEMENT  ).
Suction and discharge pressures are both low and none of the refrigerant lines are cold There is no frost on the expansion valve, and the low-pressure liquid line is not cold. The A/C system has a leak (very low refrigerant charge) Do the refrigerant leak check (see REFRIGERANT LEAK CHECK  ), repair any leaks, and recharge the A/C system (see SYSTEM CHARGING  ).
Suction and discharge pressures are both low, and the expansion valve or the suction line is abnormally cold
  • The temperature around the expansion valve is too low compared to the temperature around the receiver/dryer.
  • The low pressure (suction) hose/line is cooler than the evaporator.
  • The discharge hose/line is clogged or kinked, which is restricting refrigerant flow
  • The suction hose/line is clogged or kinked, which is restricting refrigerant flow
 Repair or replace the faulty A/C line (see A/C LINE REPLACEMENT  ).
Initially, the suction and discharge pressure are normal, but both become abnormally low during operation During extended operation, the air flow from the vents decreases. The evaporator is freezing up Run the fan with A/C compressor off to warm the evaporator, then test the evaporator temperature sensor (see EVAPORATOR TEMPERATURE SENSOR REPLACEMENT  ). If necessary, replace the evaporator temperature sensor (see EVAPORATOR TEMPERATURE SENSOR REPLACEMENT  ).
Suction and discharge pressures are both low and there are abnormal temperature changes at the expansion valve
  • During extended operation, warm air comes out of the vents, the suction pressure decreases, and heavy frost occurs on the low pressure liquid line.
  • The low pressure liquid line is cold at the expansion valve, but warm after the valve.
  • There is frost on the expansion valve.
 The expansion valve is stuck closed
The discharge pressure is low, the suction pressure is extremely low, and the expansion valve outlet is abnormally warm There is no frost on the expansion valve outlet, and the liquid line temperature changes significantly across the expansion valve. There is excessive moisture in the A/C system Recover refrigerant (see REFRIGERANT RECOVERY  ), then replace the receiver/dryer (see RECEIVER/DRYER DESICCANT REPLACEMENT  ). Evacuate the system (see REFRIGERANT RECOVERY  ), and recharge the system (see SYSTEM CHARGING  ).
The discharge pressure is low, the suction pressure is extremely low, and the suction line is abnormally cold There is frost on the line from the evaporator to the A/C compressor. The evaporator is internally contaminated or plugged Recover refrigerant (see REFRIGERANT RECOVERY  ), then replace the evaporator. Evacuate the system (see REFRIGERANT RECOVERY  ), and recharge the system (see SYSTEM CHARGING  ).
The discharge pressure is low, the suction pressure is extremely low, and the refrigerant temperature doesn't change going through the expansion valve
  • There is no frost on the expansion valve, and the low pressure liquid line is not cold.
  • The liquid line temperatures are similar on both sides of expansion valve.
 The expansion valve is faulty Replace the expansion valve (see A/C COMPRESSOR REPLACEMENT  ).
The discharge pressure is low, the suction pressure is extremely low, and the expansion valve is abnormally cold There is frost on the expansion valve. Excessive moisture in the system is freezing the expansion valve Recover refrigerant (see REFRIGERANT RECOVERY  ), the replace the receiver/dryer. Evacuate the system (see REFRIGERANT RECOVERY  ), and recharge the system (see SYSTEM CHARGING  ).
The discharge pressure is low, the suction pressure is extremely low, and the high pressure liquid line is abnormally cold There is frost on the line from the receiver/dryer to the expansion valve. The receiver/dryer is clogged Recover refrigerant (see REFRIGERANT RECOVERY  ), then replace the receiver/dryer. Evacuate the system (see REFRIGERANT RECOVERY  ), and recharge the system (see SYSTEM CHARGING  ).
Discharge pressure is so high that the A/C compressor relief valve has opened. Suction pressure is normal or below normal The temperature drop between the A/C condenser inlet and outlet is less than 30°F (-1°C) or more than 60°F (15°C) The A/C condenser or receiver/dryer is restricted Replace the restricted component, either the A/C condenser (see A/C CONDENSER REPLACEMENT  ) or the receiver/dryer (see RECEIVER/DRYER DESICCANT REPLACEMENT  ).
Discharge pressure is so high that the A/C compressor relief valve has opened. Suction pressure is also above normal
  • No evidence of restricted refrigerant flow.
  • The A/C compressor clutch stays engaged with the A/C switch off.
 The A/C compressor clutch circuit is always on (energized), or the A/C compressor clutch is mechanically jammed.
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