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Refrigerant System Tests

WARNING: This page is about a different car, the 2003 Ford RV Cutaway, 2003 Ford Econoline, 2003 Ford E550 Super Duty, 2003 Ford E450 Super Duty, and 2003 Ford Cutaway. However, it is still accessible from the selected car via links, so may be relevant.
  1. Connect an A/C recovery and/or charging station with gauges, or Connect an R134a manifold gauge set to the refrigerant system. For additional information, refer to MANIFOLD GAUGE SET CONNECTION  .
  2. Set the climate control system to MAX A/C (if equipped), or select A/C and RECTRC (if equipped), at HI blower.
    3. NOTE: When the ambient temperature exceeds 38°C (100°F), do not run the engine above normal idle speed.
  3. Run the engine at 1500 rpm for 10 minutes.
  4. Stabilize the vehicle interior temperature at 21°C to 27°C (70°F to 80°F).
  5. Record the high and low system pressures using the R134a Manifold Gauge Set, and refer to the table below.
LOW (SUCTION) PRESSURE CHART

High (Discharge) Pressure Low (Suction) Pressure Clutch Cycle Time Component - Causes
Rate  On  Off 
High High Continuous run Condenser - inadequate airflow.
High Normal to high Continuous run Engine overheating.
Normal to high Normal Continuous run Refrigerant overcharge(1) Air in refrigerant. Humidity or ambient temperature very high(2) .
Normal High Continuous run Fixed orifice tube - missing O-rings leaking/missing.
Normal Normal Slow or no cycle Long or continuous Normal or no cycle Moisture in refrigerant system. Excessive refrigerant oil.
Normal Low Slow Long Long A/C cycling switch.
Normal to low High Continuous run Compressor - low performance.
Normal to low Normal to high Continuous run A/C suction line - partially restricted or plugged(3) .
Normal to low Normal Fast Short Normal Evaporator - low or restricted airflow.
Normal to low Normal Fast Short to very short Normal to long Condenser, fixed orifice tube, or A/C liquid line - partially restricted or plugged.
Normal to low Normal Fast Short to very short Short to very short Low refrigerant charge.
Normal to low Normal Fast Short to very short Long Evaporator core - partially restricted or plugged.
Normal to low Low Continuous run A/C suction line - partially restricted or plugged(4) . A/C cycling switch - sticking closed.
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 A/C Electrical Circuit Wiring Diagram.
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) Compressor may make noise on initial run. This is slugging condition caused by excessive liquid refrigerant.

(2) Compressor clutch may not cycle in ambient temperatures above 80°F depending on humidity conditions.

(3) Low pressure reading will be normal to high if pressure is taken at accumulator and if restriction is downstream of service access valve.

(4) 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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