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Home >> GMC >> 2018 >> Acadia Denali, FWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 238 (HVAC System - Automatic) >> Diagnostic Information and Procedures >> DTC P0645, P0646, or P0647: Air Conditioning (A/C) Compressor Clutch Relay Control >> Component Testing

Component Testing

WARNING: This page is about a different car, the 2017 Cadillac ATS. However, it is still accessible from the selected car via links, so may be relevant.
  1. Ignition OFF, disconnect the KR29 A/C Compressor Clutch Relay.
  2. Test for 60-180 Ω between terminals 85 and 86.
    • If not between 60-180 Ω 

      Replace the KR29 A/C Compressor Clutch Relay.

    • If between 60-180 Ω 
  3. Test for infinite resistance between the terminals listed below:
    • 30 and 86
    • 30 and 87
    • 30 and 85
    • 85 and 87
    • If less than infinite resistance 

      Replace the KR29 A/C Compressor Clutch Relay.

    • If infinite resistance 
  4. Install a 15 A fused jumper wire between terminal 86 and 12 V. Install a jumper wire between terminal 85 and ground.
  5. Test for less than 2 Ω between terminals 30 and 87.
    • If 2 Ω or greater 

      Replace the KR29 A/C Compressor Clutch Relay.

    • If less than 2 Ω 
  6. All OK.
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