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Home >> Chevrolet >> 2020 >> Express 2500 LS, 6.0L Eng VIN G >> Repair and Diagnosis >> External Pages >> Different car >> Section 79 (HVAC - Manual) >> Diagnostic Information and Procedures >> DTC P0645, P0646, or P0647 >> Component Testing

Component Testing

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  1. Ignition OFF, disconnect the A/C compressor clutch relay.
  2. Test for 60 - 180 ohms between terminals 85 and 86.
    • If the resistance is not within the specified range, replace the relay.
  3. Test for infinite resistance between the following terminals:
    • 30 and 86
    • 30 and 87
    • 30 and 85
    • 85 and 87
    • If not the specified value, replace the relay.
  4. Install a 30-amp fused jumper wire between relay terminal 85 and 12 volts. Install a jumper wire between relay terminal 86 and ground. Test for less than 2 ohms between terminals 30 and 87.
    • If greater than the specified range, replace the relay.
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