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Electronic Control Module (ECM) Compressor Control Test

  1. Ensure ignition is off. Disconnect ECM 24-pin connector. ECM is located behind right kick panel. Ensure A/C compressor is connected. Turn ignition switch to RUN (engine off) position.
  2. Set air control knob to bi-level. For proper test results, temperature outside of vehicle must be 60°F (16°C) or more. Using a DVOM, measure voltage between ground and Brown wire (terminal B8) of ECM connector. If battery voltage is present, go to next step. If battery voltage is not present, check Brown wire for open. Repair wiring as necessary.
  3. Measure voltage between ground and Blue wire of ECM connector. If battery voltage is present, go to next step. If battery voltage is not present, check Blue wire for open. Repair wiring as necessary. If Blue wire is okay, replace A/C compressor relay.
  4. Connect a fused jumper wire between ground and Blue wire of ECM connector. With fused jumper wire connected, A/C compressor relay should operate and A/C compressor clutch should engage.
  5. If relay does not operate and compressor clutch does not engage, replace A/C compressor relay. If relay and compressor clutch operate properly, but A/C system still malfunctions, problem may be caused by faulty ECM.
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