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Home >> Jeep >> 2000 >> Cherokee Classic, 4D Utility, 4WD, Part Time >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Self Diagnostics >> Diagnostic Tests >> DTC P0645: A/C Clutch Relay Circuit >> Testing

DTC P0645: A/C Clutch Relay Circuit: Testing

  1. Turn ignition on, with engine off. Using scan tool, actuate A/C clutch relay. A/C clutch relay is located in Power Distribution Center (PDC). PDC is located in engine compartment, next to battery. See Figure . If A/C clutch relay clicks, go to next step. If A/C clutch relay does not click, go to step  4 .
  2. Ensure ignition is on, with engine off. Wiggle wiring harness from A/C clutch relay to PCM while actuating A/C clutch relay. PCM is located in engine compartment on left front fender, near radiator support. If A/C clutch relay stops clicking at any time while wiggling wiring harness, repair wiring harness where wiggling caused A/C clutch relay to stop clicking. If A/C clutch relay does not stop clicking at any time while wiggling wiring harness, go to next step.
  3. Turn ignition off. Visually inspect related connectors and wiring harness. Repair connectors and wiring harness as necessary. If connectors and wiring harness are okay, no problem is indicated at this time. Test is complete.
  4. Turn ignition off. Remove A/C clutch relay. A/C clutch relay is located in Power Distribution Center (PDC). PDC is located in engine compartment, next to battery. See Figure . Measure voltage between ground and terminal B5 (White wire) at A/C clutch relay socket in PDC. See Figure . If voltage is more than 10 volts, go to next step. If voltage is 10 volts or less, repair open in fused ignition switch output circuit (White wire) to A/C clutch relay. See WIRING DIAGRAMS article.
  5. Measure resistance between terminals No. 85 and 86 at A/C clutch relay. See Figure . If resistance is less than 100 ohms, go to next step. If resistance is 100 ohms or more, replace A/C clutch relay.
  6. Ensure ignition is off. Disconnect PCM connectors. PCM is located in engine compartment on left front fender, near radiator support. Inspect connectors for damaged pins, corrosion and loose terminals. Repair connectors as necessary. If connectors are okay, measure resistance of Dark Blue/Orange wire between terminal B3 at A/C clutch relay socket in PDC and terminal No. 1 at PCM C3 connector. See Figure and Figure . If resistance is less than 5 ohms, go to next step. If resistance is 5 ohms or more, repair open in Dark Blue/Orange wire between A/C clutch relay and PCM.
  7. Measure resistance between ground and Dark Blue/Orange wire at terminal No. 1 at PCM C3 connector. If resistance is less than 5 ohms, repair short to ground in Dark Blue/Orange wire. If resistance is 5 ohms or more, go to next step.
  8. At this time, PCM is assumed to be defective. Replace PCM.
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