Compressor Clutch: Testing and Inspection

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 totally integrated power module (TIPM) Operation. Begin testing of a suspected compressor clutch coil problem by performing the preliminary checks.

PRELIMINARY CHECKS

1. Using a scan tool, check for diagnostic trouble codes (DTCs) in the A/C-heater control, TIPM and the PCM/ECM. If no DTCs are found, 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 Refrigerant System Leak Test. 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. 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 COIL CURRENT DRAW TEST and/or COIL RESISTANCE TEST - 2.8L AND 4.0L ENGINES ONLY.
COIL CURRENT DRAW TEST

4. Verify the battery state of charge Battery.
5. Connect an ammeter (0 to 10 ampere scale selected) in series with the clutch field coil feed terminal. Connect a voltmeter (0 to 20 volt scale selected) to measure voltage across the battery and the clutch coil.
6. 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.
7. The A/C clutch should engage immediately, and the clutch field coil supply voltage should be within two volts of the battery voltage. If the field coil supply voltage is OK, go to STEP 5. If the field coil supply voltage is not within two volts of battery voltage, test the clutch field coil feed circuit for excessive voltage drop and repair as necessary.
8. Refer to the following A/C Clutch Field Coil Specifications chart for the acceptable A/C clutch field coil current draw. 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 field coil current reading is zero, the coil is open and must be replaced.
b. If the A/C clutch field coil current reading is above specifications, the coil is shorted and must be replaced.
COIL RESISTANCE TEST - 2.8L AND 4.0L ENGINES ONLY

9. Disconnect and isolate the negative battery cable.
10. Disconnect the wire harness connector from the A/C clutch field coil connector.
11. Use an ohmmeter and measure the resistance of the clutch field coil at the field coil connector terminals.
12. Refer to the following A/C Clutch Field Coil Specifications chart for the acceptable A/C clutch coil resistance.
a. If the A/C clutch coil resistance reading is above specifications, the coil is shorted and must be replaced.
b. If the A/C clutch coil resistance reading is below specifications, the coil is open and must be replaced.