REFRIGERANT > ON-VEHICLE INSPECTION

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1. INSPECT REFRIGERANT VOLUME


  1. Check the sight glass on the air conditioning tube & accessory assembly.


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    1. Prepare the vehicle according the chart below.
      Item
      		Condition
      Vehicle door
      		Fully open
      Temperature setting
      		MAX COLD
      Blower speed
      		HI
      A/C
      		ON

    2. Compare the sight glass to the following chart.

      Item
      		Symptom
      		Amount of refrigerant
      		Corrective Actions
      1
      		Bubbles exist
      		Insufficient*
      1. Check for gas leakage and repair if necessary
      2. Add refrigerant until bubbles disappear
      2
      		No bubbles exist (DTC 76 is output)
      		Empty, insufficient or excessive
      		Refer to 3 and 4
      3
      		No temperature difference between compressor inlet and outlet
      		Empty or nearly empty
      1. Check for gas leakage and repair if necessary
      2. Evacuate the AC system and recharge the proper amount of refrigerant
      4
      		Considerable temperature difference between compressor inlet and outlet.
      		Proper or excessive
      		Refer to 5 and 6
      5
      		Immediately after air conditioning is turned off, refrigerant remains clear
      		Excessive
      1. Discharge refrigerant
      2. Evacuate the AC system and recharge the proper amount of refrigerant
      6
      		Immediately after air conditioning is turned off, refrigerant foams and then becomes clear
      		Proper
      		-
      *: Bubbles in the sight glass with the vehicle's interior above 35°C (95°F) can be considered normal if cooling is sufficient.



2. INSPECT REFRIGERANT PRESSURE WITH MANIFOLD GAUGE SET

HINT:
This is a method where a manifold gauge set is used to help locate the problem.



  1. Read the manifold gauge pressure when these conditions are established.
    Test conditions:

    1. Temperature at the air inlet with the switch set at RECIRC is 30 to 35°C (86 to 95°F)
    2. Engine is running at 1,500 rpm
    3. Blower speed control switch is at "HI"
    4. Temperature control dial is at "COOL"
    5. A/C switch is ON
    6. Doors are fully open
    7. Ignition switch in a position that enables the AC compressor to run.



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    1. Normally functioning refrigeration system

      Gauge reading:
      Low pressure side:
      0.15 to 0.25 MPa (1.5 to 2.5 kgf/cm2, 21.3 to 35.5 psi)
      High pressure side:
      1.37 to 1.57 MPa (14 to 16 kgf/cm2, 199.1 to 227.5 psi)



    2. Moisture is present in refrigeration system.


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      Symptom
      		Probable cause
      		Diagnosis
      		Corrective Actions
      During operation, pressure on low pressure side cycles between normal and vacuum
      		Moisture in AC system will freeze at the expansion valve orifice, causing the refrigeration cycle to temporarily stop
      After the system stop, and warms up again, the ice will melt and normal operation will be temporarily restored
      1. Dryer in oversaturated state
      2. Moisture in refrigeration system freezes at expansion valve orifice and blocks circulation of refrigerant
      1. Replace condenser
      2. Remove moisture in system by repeatedly evacuating air
      3. Supply a proper amount of new refrigerant



    3. Insufficient cooling


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      Symptom
      		Probable cause
      		Diagnosis
      		Corrective Actions
      1. Pressure is low on both low and high pressure sides
      2. Bubbles are seen through sight glass continuously
      3. Insufficient cooling performance
      		Gas leakage from the refrigeration system
      1. Insufficient refrigerant
      2. Refrigerant leaking
      1. Check for gas leakage and repair if necessary
      2. Supply a proper amount of new refrigerant
      3. If the gauge indicates a pressure of close to 0, then it will be necessary to evacuate the system after repairing the leak



    4. Poor circulation of refrigerant


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      Symptom
      		Probable cause
      		Diagnosis
      		Corrective Actions
      1. Pressure is low on both low and high pressure sides
      2. Frost exists on pipe from condenser to unit
      		Refrigerant flow is obstructed by dirt inside the pipes of the condenser core
      		Receiver is clogged
      		Replace condenser



    5. Refrigerant does not circulate.


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      Symptom
      		Probable cause
      		Diagnosis
      		Corrective Actions
      1. Vacuum is indicated on low pressure side and very low pressure is indicated on high pressure side
      2. Frost or condensation is seen on piping on both sides of receiver/drier or expansion valve
      1. Refrigerant flow is obstructed by moisture or dirt in refrigeration system
      2. Refrigerant flow is disrupted by gas leaking internally through the expansion valve
      		Refrigerant does not circulate
      1. Check the expansion valve
      2. Replace expansion valve
      3. Replace condenser
      4. Evaporate air and supply a proper amount of new refrigerant
      5. For internal gas leak at expansion valve, replace expansion valve



    6. Refrigerant is overcharged or cooling effectiveness of condenser is insufficient.


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      Symptom
      		Probable cause
      		Diagnosis
      		Corrective Actions
      1. Pressure is too high on both low and high pressure sides
      2. No air bubbles are seen through sight glass even when engine rpm lowers
      1. Unable to develop sufficient performance due to excessive use of refrigeration system
      2. Cooling effectiveness of condenser is insufficient
      1. Excessive refrigerant in cycle → excessive refrigerant was recharged
      2. Condenser cooling effectiveness is insufficient → condenser fins are clogged at cooling fan
      1. Clean condenser
      2. Check the operation of the condenser cooling fan
      3. If 1 and 2 are normal state, check the amount of refrigerant and supply proper amount of refrigerant



    7. Air is present in refrigeration system.


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      Symptom
      		Probable cause
      		Diagnosis
      		Corrective Actions
      1. Pressure is too high on both low and high pressure sides
      2. The low pressure piping is too hot to touch
      3. Bubbles can be seen through sight glass
      		Air in system
      1. Air present in refrigeration system
      2. Insufficient vacuum purging
      1. Check compressor oil to see if it is dirty or insufficient
      2. Evacuate the system and recharge it with new or purified refrigerant



    8. Expansion valve malfunction


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      Symptom
      		Probable cause
      		Diagnosis
      		Corrective Actions
      1. Pressure is too high on both low and high pressure sides
      2. Frost or a large amount of condensation on piping on low pressure side
      		Expansion valve may be sticking
      1. Excessive refrigerant in low pressure piping
      2. Expansion valve opened too wide
      		Check expansion valve



    9. Insufficient compressor compression


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      Symptom
      		Probable cause
      		Diagnosis
      		Corrective Actions
      1. Pressure is too high both on low and high pressure sides
      2. Pressure is too low on high pressure side
      		Internal leak in compressor
      1. Low compression
      2. Leak from a damaged valve, or parts may be broken
      		Replace compressor
      Gauge readings (Reference)


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