REFRIGERANT(for HFC-134a(R134a)) ON-VEHICLE INSPECTION

PROCEDURE

  1. INSPECT REFRIGERANT PRESSURE WITH MANIFOLD GAUGE SET

    Tip:

    The following examples show the readings of a manifold gauge set and the corresponding air conditioning system problems.

    1. Read the manifold gauge pressure when the following conditions are met:

      • Doors are fully open.

      • The engine is idling.

      • The A/C switch is on.

      • The temperature is set to max cool.

      • The blower speed is set to high.

      • Temperature at the air inlet with recirculate selected is 30 to 35°C (86 to 95°F).

      1. E268307

        Normally functioning air conditioning system

        Table 1. Gauge Reading

        Pressure Side

        Refrigerant Volume

        Low

        0.15 to 0.25 MPa (1.5 to 2.5 kgf/cm2, 21 to 36 psi)

        High

        1.37 to 1.57 MPa (14 to 16 kgf/cm2, 199 to 228 psi)

      2. Abnormally functioning air conditioning system

        1. E225742C10

          *a

          LO

          *b

          HI

          During operation, pressure on low pressure side cycles between normal and vacuum

          Symptom

          Air conditioning system periodically cools and then fails to cool

          Probable Cause

          Moisture in air conditioning system freezes at expansion valve orifice, causing refrigerant to temporarily stop circulating

          After system stops and warms up again, ice melts and normal operation is temporarily restored

          Diagnosis

          Cooler dryer (integrated into condenser tank) saturated with moisture

          Moisture in air conditioning system is freezing at expansion valve orifice and blocking circulation of refrigerant

          Corrective Actions

          Replace cooler dryer

          Remove moisture by repeatedly evacuating air from air conditioning system

          Recharge air conditioning system with proper amount of new or purified refrigerant
          Tip:

          For the example above, moisture is present in the air conditioning system.

        2. E225743C10

          *a

          LO

          *b

          HI

          Pressure is low on both low and high pressure sides

          Symptom

          Air conditioning system does not cool effectively

          Insufficient cooling performance

          Probable Cause

          Refrigerant leaks from air conditioning system

          Diagnosis

          Insufficient refrigerant

          Refrigerant leaking

          Corrective Actions

          Check for refrigerant leaks and repair if necessary

          Recharge air conditioning system with proper amount of new or purified refrigerant

          If gauges indicate pressure of close to 0, then it is necessary to evacuate air conditioning system after repairing leaks
          Tip:

          For the example above, there is insufficient refrigerant.

        3. E225744C10

          *a

          LO

          *b

          HI

          Pressure is low on both low and high pressure sides

          Symptom

          Air conditioning system does not cool effectively

          Frost exists on pipe from condenser to evaporator unit

          Probable Cause

          Refrigerant flow is obstructed by dirt inside pipes of condenser core

          Diagnosis

          Condenser is clogged

          Corrective Actions

          Replace condenser
          Tip:

          For the example above, there is poor circulation of refrigerant.

        4. E225745C10

          *a

          LO

          *b

          HI

          Vacuum is indicated on low pressure side and very low pressure is indicated on high pressure side

          Symptom

          Air conditioning system does not cool effectively (System may cool occasionally)

          Frost or condensation is seen on piping on both sides of receiver/dryer or expansion valve

          Probable Cause

          Refrigerant flow is obstructed by moisture or dirt in air conditioning system

          Expansion valve is stuck closed

          Diagnosis

          Refrigerant does not circulate

          Corrective Actions

          Replace expansion valve

          Replace condenser

          Evacuate air conditioning system and recharge with proper amount of new or purified refrigerant
          Tip:

          For the example above, the refrigerant does not circulate.

        5. E225746C10

          *a

          LO

          *b

          HI

          Pressure is too high on both low and high pressure sides

          Symptom

          Air conditioning system does not cool effectively

          Probable Cause

          Unable to provide sufficient performance due to excessive amount of refrigerant

          Cooling effectiveness of condenser is insufficient

          Diagnosis

          Excessive amount of refrigerant in air conditioning system because excessive refrigerant was added during recharging

          Cooling effectiveness of condenser is insufficient because condenser fins are clogged or cooling fan is faulty

          Corrective Actions

          Clean condenser

          Check operation of condenser cooling fan

          If condenser is clean and fan operation is normal, check amount of refrigerant and recharge air conditioning system with proper amount of new or purified refrigerant
          Tip:

          For the example above, the air conditioning system is overcharged or cooling effectiveness of condenser is insufficient.

        6. E225747C09

          *a

          LO

          *b

          HI

          Pressure is too high on both low and high pressure sides

          Symptom

          Air conditioning system does not cool

          The low pressure piping is too hot to touch

          Probable Cause

          Air in air conditioning system

          Diagnosis

          Air present in air conditioning system

          Insufficient vacuum purging when evacuating air conditioning system

          Corrective Actions

          Replace cooler dryer

          Check compressor oil to see if it is dirty or insufficient

          Evacuate air conditioning system and recharge it with new or purified refrigerant
          Note:

          These gauge indications occur when the air conditioning system has been left open and then recharged without evacuating the system.

          Tip:

          For the example above, air is present in the air conditioning system.

        7. E225748C10

          *a

          LO

          *b

          HI

          Pressure is too high on both low and high pressure sides

          Symptom

          Air conditioning system does not cool effectively

          Frost or large amount of condensation on piping on low pressure side

          Probable Cause

          Expansion valve may be stuck open or metering refrigerant incorrectly

          Diagnosis

          Excessive refrigerant in low pressure piping

          Expansion valve open too wide

          Corrective Actions

          Replace expansion valve
          Tip:

          For the example above, there is an expansion valve malfunction.

        8. E225749C09

          *a

          LO

          *b

          HI

          Pressure is too high on both low and high pressure sides or pressure is too low on high pressure side

          Symptom

          Air conditioning system does not cool effectively

          Probable Cause

          Internal leak in compressor

          Diagnosis

          Low compression

          Leak from damaged valve or other compressor component

          Corrective Actions

          Replace compressor
          Tip:

          For the example above, there is insufficient compressor compression.

      3. Gauge readings (Reference)

        E268295C01

        *a

        Pressure on Low Pressure Side MPa (kgf/cm2, psi)

        *b

        Pressure on High Pressure Side MPa (kgf/cm2, psi)

        *c

        Blower High Zone

        *d

        Blower Low Zone