A/C Compressor Clutch Coil

The A/C compressor clutch coil electrical circuit is controlled by the powertrain control module (PCM) or the engine control module (ECM) (depending on engine application) through the A/C clutch relay. Begin testing of a suspected compressor clutch coil problem by performing the preliminary checks.

PRELIMINARY CHECKS
1. If no diagnostic trouble codes (DTCs) are found in the powertrain control module (PCM) or the engine control module (ECM) (depending on engine application), go to Step 2. If any DTCs are found, repair as required.
2. If the A/C compressor clutch still will not engage, verify the refrigerant charge level. If the refrigerant charge level is OK, go to Step 3. If the refrigerant charge level is not OK, adjust the refrigerant charge as required.
3. On models equipped with the 2.4L or 3.7L gasoline engine, if the A/C compressor clutch still will not engage, disconnect the wire harness connector from the A/C pressure transducer and check for battery current at the connector with the engine running and the A/C-heater control set to the A/C mode. If OK, go to TESTS. If not OK, refer to the Body Diagnostic Procedures to perform further diagnosis. On models equipped with the 2.8L diesel engine, go to TESTS.

TESTS
1. Verify the battery state of charge.
2. Connect an ammeter (0 to 10 ampere scale selected) in series with the clutch coil feed terminal. Connect a voltmeter (0 to 20 volt scale selected) to measure voltage across the battery and the clutch coil.
3. With the A/C-heater control in the A/C mode and the blower motor at low speed, start the engine and allow it to run at a normal idle speed.
4. The A/C compressor clutch should engage immediately, and the clutch coil supply voltage should be within two volts of the battery voltage. If the coil supply voltage is OK, go to Step 5. If the coil supply voltage is not within two volts of battery voltage, test the clutch coil feed circuit for excessive voltage drop and repair as necessary. 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 and PCM control. The following components must be checked and repaired as required before you can complete testing of the clutch coil:
- Fuses in the junction block (JB) and the power distribution center (PDC)
- A/C heater mode control
- A/C clutch relay
- A/C high pressure switch (diesel engine)
- A/C low pressure switch
- Powertrain control module (PCM) or the engine control module (ECM) (depending on engine application)

5. For the acceptable A/C clutch coil current draw specifications refer to HEATING & AIR CONDITIONING - SPECIFICATIONS. Specifications apply for a work area temperature of 21° C (70° F). If voltage is more than 12.5 volts, add electrical loads by turning on electrical accessories until voltage reads below 12.5 volts.
a. If the A/C clutch coil current reading is zero, the coil is open and must be replaced.
b. If the A/C clutch coil current reading is above specifications, the coil is shorted and must be replaced.