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Test P: Insufficient A/C Cooling

WARNING: This page is about a different car, the 1999 Lincoln Navigator and 1999 Ford Expedition. However, it is still accessible from the selected car via links, so may be relevant.

  1. Vehicle Set-Up

    Connect manifold gauge set. Start and run engine at 1500 RPM. Set EATC panel to MAX A/C position. Set blower/fan on high speed and close doors and windows. Insert thermometer in center vent. Operate system for 10-15 minutes to allow system to stabilize. When vehicle has stabilized, proceed with tests.

  2. Check Center Register Discharge Temperature

    Check and record center register and ambient temperature. Compare readings with AMBIENT/CENTER REGISTER TEMPERATURE SPECIFICATIONS  table. If readings are within specifications, system is functioning normally. If readings are not within specifications, go to next step.
    AMBIENT/CENTER REGISTER TEMPERATURE SPECIFICATIONS

    Ambient Temp. °F (°C) Center Register Temp. °F (°C)
    60 (16) 33-47 (0.6-8)
    70 (21) 33-47 (0.6-8)
    80 (27) 33-47 (0.6-8)
    90 (32) 33-47 (0.6-8)
    100 (38) 36-48 (2-9)

  3. Check For Normal Discharge Pressure

    Check and record ambient temperature and compressor discharge (high) pressure. Compare readings with AMBIENT TEMPERATURE/DISCHARGE PRESSURE SPECIFICATIONS  table. If readings are within specifications, go to next step. If readings are not within specifications, go to step 9)  .
    AMBIENT TEMPERATURE/DISCHARGE PRESSURE SPECIFICATIONS

    Ambient Temp. °F (°C) Discharge Pressure psi (kg/cm2 )
    60 (16) 75-175 (5-12)
    70 (21) 100-200 (7-14)
    80 (27) 125-225 (9-16)
    90 (32) 150-250 (11-18)
    100 (38) 175-350 (12-25)

  4. Check Low Pressure Performance

    Check and record ambient temperature and compressor suction (low) pressure. Compare readings with AMBIENT TEMPERATURE/SUCTION PRESSURE SPECIFICATIONS  table. If readings are within specifications, go to next step. If readings are not within specifications, go to step 7)  .
    AMBIENT TEMPERATURE/SUCTION PRESSURE SPECIFICATIONS

    Ambient Temp. °F (°C) Suction Pressure psi (kg/cm2 )
    60 (16) 24-45 (2-3)
    70 (21) 24-45 (2-3)
    80 (27) 24-45 (2-3)
    90 (32) 24-45 (2-3)
    100 (38) 38-60 (3-4)

  5. Check For Slow Or Continuous Run Clutch Cycle Rate

    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. If readings are above upper limit of specification, go to next step. If readings are within specification, repair evaporator core for partial restriction or plugged condition. Retest system.
    AMBIENT TEMPERATURE/CLUTCH CYCLE TIME SPECIFICATIONS

    Ambient Temp. °F (°C) Clutch Cycle Time (Seconds)
    60 (16) 28-50
    70 (21) 30-65
    80 (27) 45-120
    90 (32) 95-Continuous

  6. Check For Long Or Continuous Clutch Off Time

    Check and record ambient temperature and total compressor off time in seconds. Compare readings with AMBIENT TEMPERATURE/CLUTCH OFF TIME SPECIFICATIONS  table. If readings are above upper limit of specification, repair system for excessive moisture or refrigerant oil condition. Retest system. If readings are within specification, go to step 8)  .
    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

  7. Check For High Suction Pressure

    If readings in step 4)  are above upper limit of specification, repair evaporator core orifice for missing or damaged (leaking) "O" rings. Retest system. If readings in step 4)  are not above upper limit of specification, replace A/C cycling switch for low cut-out condition. Retest system.

  8. Check Ambient Temperature

    Refer to readings obtained in step 6)  . If ambient temperature is above 80°F (27°C), this is normal operation for refrigerant system in high humidity conditions. If ambient temperature is not above 80°F (27°C), repair system for overcharge condition. Retest system.

  9. Check For High Discharge Pressure

    Refer to readings obtained in step 3)  . If reading is above upper limit of specification, go to next step. If reading is not above upper limit of specification, go to step 12)  .

  10. Check For Normal Low Pressure

    Check and record ambient temperature and compressor suction (low) pressure. Compare readings with AMBIENT TEMPERATURE/SUCTION PRESSURE SPECIFICATIONS  table. If readings are within specifications, repair engine for overheating condition. Retest system. If readings are not within specifications, go to next step.

  11. Check For Normal-To-Low Section Pressure

    Refer to readings obtained in step 10)  . If reading is below lower limit of specification, repair evaporator core orifice for partially restricted or plugged condition. Retest system. If reading is not below lower limit of specification, repair condenser core for partially blocked or inadequate airflow condition. Retest system.

  12. Check For Normal Suction Pressure

    Check and record ambient temperature and compressor suction (low) pressure. Compare readings with AMBIENT TEMPERATURE/SUCTION PRESSURE SPECIFICATIONS  table. If readings are within specification, go to next step. If readings are not within specification, go to step 16)  .

  13. Check For Slow Clutch Cycle Rate

    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. If readings are above upper limit of specification, repair evaporator-to-compressor suction line for partially restricted or plugged condition. Retest system. If readings are within specification, go to next step.

  14. Check For Normal Clutch Off Time

    Check and record ambient temperature and total compressor off time in seconds. Compare readings with AMBIENT TEMPERATURE/CLUTCH OFF TIME SPECIFICATIONS  table. If reading is within specifications, repair evaporator core for low or restricted air flow. Retest system. If readings are not within specifications, go to next step.

  15. Check For Long Clutch Off Time

    Refer to readings obtained in step 14)  . If reading is above upper limit of specification, repair condenser core for partially or plugged condition. Retest system. If reading is not above upper limit specification, repair system for low refrigerant condition.

  16. Check For Missing Evaporator Core Orifice

    Discharge A/C system, using approved refrigerant recovery/recycling equipment. Remove condenser-to-evaporator tube. Check for presence of fixed orifice tube. If fixed orifice tube is missing, install Orange colored orifice tube. Retest system. If fixed orifice tube is not missing, repair A/C compressor for low performance. Retest system.
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