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A/C System Performance

  1. Park vehicle out of direct sunlight. Connect manifold gauge set. Start and run engine at 1500 RPM. Set A/C controls to MAX A/C. Set blower on high speed. Insert thermometer in center vent and stabilize in-car temperature at 70-80°F (21-27°C). Maintain engine speed at 1500 RPM.
  2. Check and record ambient temperature and compressor discharge (high) pressure. Compare readings with AMBIENT TEMPERATURE/DISCHARGE PRESSURE SPECIFICATIONS  table. With ambient temperatures of 100-110°F (38-43°C), system performance pressures will be the same as those for ambient temperatures of 90-100°F (32-38°C). System performance is acceptable between upper and lower limits.
  3. Check and record ambient temperature and compressor suction (low) pressure. Compare readings with AMBIENT TEMPERATURE/SUCTION PRESSURE SPECIFICATIONS  table. With ambient temperatures of 100-110°F (38-43°C), system performance pressures will be the same as those for ambient temperatures of 90-100°F (32-38°C). System performance is acceptable between upper and lower limits.
  4. Check and record ambient temperature and compressor clutch on time in seconds. Compare readings with AMBIENT TEMPERATURE/CLUTCH ON TIME SPECIFICATIONS  table. When ambient temperature is above 80°F (27°C), A/C compressor clutch may not cycle. System performance is acceptable between upper and lower limits.
  5. Check and record ambient temperature and compressor off time in seconds. Compare readings with AMBIENT TEMPERATURE/CLUTCH OFF TIME SPECIFICATIONS  table. When ambient temperature is above 80°F (27°C), A/C compressor clutch may not cycle. System performance is acceptable between upper and lower limits.
    AMBIENT TEMPERATURE/CLUTCH ON TIME SPECIFICATIONS

    Ambient Temp. °F (°C) Clutch On Time (Seconds)
    60 (16) 10-25
    70 (21) 20-45
    80 (27) 40-100
    90 (32) 90-Continuous
    AMBIENT TEMPERATURE/CLUTCH OFF TIME SPECIFICATIONS

    Ambient Temp. °F (°C) Clutch Off Time (Seconds)
    60 (16) 17-24
    70 (21) 14-23
    80 (27) 2-17
    90 (32) 2-3
  6. Check and record ambient temperature and total compressor clutch cycle time (time on plus time off) in seconds. Compare readings with AMBIENT TEMPERATURE/CLUTCH CYCLE TIME SPECIFICATIONS  table. When ambient temperature is above 80°F (27°C), A/C compressor clutch may not cycle. System performance is acceptable between upper and lower limits.
  7. Check and record ambient temperature and number of compressor clutch cycles occurring in one minute. Compare readings with AMBIENT TEMPERATURE/CLUTCH CYCLE RATE SPECIFICATIONS  table. When ambient temperature is above 80°F (27°C), A/C compressor clutch may not cycle. System performance is acceptable between upper and lower limits.
    AMBIENT TEMPERATURE/CLUTCH CYCLE RATE SPECIFICATIONS

    Ambient Temp. °F (°C) Clutch Cycle Rate (Per Min.)
    60 (16) 1.25-2.25
    70 (21) 1.00-2.00
    80 (27) 0.25-1.25
    90 (32) 0
  8. Check and record center register and ambient temperature. Compare readings with AMBIENT/CENTER REGISTER TEMPERATURE SPECIFICATIONS  table. With ambient temperatures of 100-110°F (38-43°C), register discharge temperatures will be the same as those for ambient temperatures of 90-100°F (32-38°C). System performance is acceptable between upper and lower limits.
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