Diagnosis And Testing - A/C Compressor Clutch Coil

For circuit descriptions and diagrams, (Refer to Appropriate Wiring Information). The battery must be fully-charged before performing the following tests (Refer to DIAGNOSIS AND TESTING--BATTERY ).

1. Connect an ammeter (0 to 10 ampere scale) in series with the clutch coil terminal. Use a voltmeter (0 to 20 volt scale) with clip-type leads for measuring the voltage across the battery and the compressor clutch coil.
2. With the a/c select button depressed, and the blower motor switch in the lowest speed position, start the engine and run it at normal idle.
3. The compressor clutch coil voltage should read within 0.2 volts of the battery voltage. If there is voltage at the clutch coil, but the reading is not within 0.2 volts of the battery voltage, test the clutch coil feed circuit for excessive voltage drop and repair as required. If there is no voltage reading at the clutch coil, use a DRB III(R) scan tool and (Refer to Appropriate Diagnostic Information) for testing of the compressor clutch circuit. The following components must be checked and repaired as required before you can complete testing of the clutch coil:
   • Fuses in the junction block and the Power Distribution Center (PDC)
   • A/C Heater Control
   • Compressor Clutch Relay
   • A/C Pressure Transducer
   • Evaporator Temperature Sensor
   • Powertrain Control Module (PCM)
4. The compressor clutch coil is acceptable if the current draw measured at the clutch coil is 2.0 to 3.9 amperes with the electrical system voltage at 11.5 to 12.5 volts. This should only be checked with the work area temperature at 21°C (70°F). If system voltage is more than 12.5 volts, add electrical loads by turning on electrical accessories until the system voltage drops below 12.5 volts.
   1. If the clutch coil current reading is four amperes or more, the coil is shorted and should be replaced.
   2. If the clutch coil current reading is zero, the coil is open and should be replaced.