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Diagnostic Table

WARNING: This page is about a different car, the 2002 Ford Windstar. However, it is still accessible from the selected car via links, so may be relevant.
    NOTE: The following table is used to guide diagnosis of the refrigerant system if operating pressures are outside normal limits.
  1. Refer to the chart below.
    A/C COMPONENTS DIAGNOSTIC ACCORDING TO REFRIGERANT DISCHARGE (HIGH) AND SUCTION (LOW) PRESSURES

    High (Discharge) Pressure Low (Suction) Pressure Component - Causes
    High or clutch cycling High Condenser - inadequate airflow.
    High Normal to high Engine - overheating.
    Normal to high Normal Refrigerant overcharge - air in refrigerant.
    Normal to low High Fixed orifice tube - missing O-rings leaking/missing.
    Normal to low Normal to high A/C suction line - partially restricted or plugged(1).
    Normal to low Low or clutch cycling Low refrigerant charge, A/C suction line - partially restricted or plugged(2) A/C cycling switch - sticking closed (if equipped).
    Erratic operation or compressor not running A/C cycling switch - poor connection at A/C clutch connector or clutch cycling switch connector. A/C electrical circuit erratic - see AIR CONDITIONING .
    Normal to low High Compressor - low performance.
    Additional Possible Cause Components Associated With Inadequate Compressor Operation 
    • Compressor drive belt - loose
    • Compressor clutch - slipping
    • Clutch coil open - shorted, or loose mounting
    • Control assembly switch - dirty contacts or sticking open
    • Clutch wiring circuit - high resistance, open or blown fuse
    • Compressor operation interrupted by engine computer
    Additional Possible Cause Components Associated With a Damaged Compressor 
    • Incorrect clutch air-gap
    • Suction accumulator - refrigerant oil bleed hose plugged
    • Refrigerant leaks
    (1) a Low pressure reading will be normal to high if pressure is taken at accumulator and if restriction is downstream of service access valve.
    (2) b Low pressure reading will be low if pressure is taken near the compressor and restriction is upstream of service access valve.
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