Compressor Clutch Coil: Testing and Inspection

For circuit descriptions and diagrams, refer to the appropriate wiring information. The wiring information includes wiring diagrams, proper wire and connector repair procedures, further details on wire harness routing and retention, as well as pin-out and location views for the various wire harness connectors, splices and grounds. Begin testing of a suspected compressor clutch coil problem by performing the preliminary checks.

PRELIMINARY CHECKS
1. If the compressor clutch will not engage, verify the refrigerant charge level. If the refrigerant charge level is OK, go to Step 2. If the refrigerant charge level is not OK, adjust the refrigerant charge as required.
2. If the a/c compressor clutch still will not engage, disconnect the headlamp and dash wire harness connector for the A/C pressure transducer and check for battery current at the connector with the engine running and the heater - A/C 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.

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 any A/C mode and the blower at the lowest speed, start the engine and allow it to run at a normal idle speed.
4. The compressor clutch should engage immediately, and the clutch coil voltage should be within two volts of the battery voltage. If the coil voltage is not within two volts of battery voltage, test the clutch coil feed circuit for excessive voltage drop. If the compressor clutch does not engage, refer to Body Diagnostic Procedures to perform further diagnosis.

The following components must be checked and repaired as required before you can complete testing of the clutch coil:
- Fuses in the fuse block and the Power Distribution Center (PDC)
- A/C-heater mode control switch
- A/C Compressor clutch relay
- A/C High pressure switch
- A/C Low pressure switch
- Powertrain Control Module (PCM)

5. With the ambient temperature at 21° C (70° F), the compressor dutch coil is acceptable if the current draw is 2.0 to 3.7 amperes at 11.5 to 12.5 volts at the clutch coil. If the voltage is more than 12.5 volts, add electrical loads by turning on electrical accessories until the voltage reads below 12.5 volts.
a. If the compressor clutch coil current reading is zero, the coil is open and must be replaced.
b. If the compressor clutch coil current reading is four amperes or more, the coil is shorted and must be replaced.

6. Remove the screw and retainer from the clutch coil lead wire harness on the compressor front housing.
7. Remove the external snap ring that secures the compressor clutch coil to the nose of the compressor front housing with snap ring pliers and slide the coil assembly off of the compressor .

INSPECTION

NOTE: The compressor clutch can be serviced in the vehicle. The refrigerant system can remain fully-charged during compressor clutch, pulley, or coil replacement.

Examine the friction surfaces of the clutch pulley and the clutch plate for wear. The pulley and plate should be replaced if there is excessive wear or scoring.
If the friction surfaces are oily, inspect the shaft and nose area of the compressor for refrigerant oil. Remove the felt wick from around the shaft inside the nose of the compressor front housing. If the felt is saturated with refrigerant oil, the compressor shaft seal is leaking and the compressor must be replaced.

Check the clutch pulley bearing for roughness or excessive leakage of grease. Replace the bearing, if required.