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Home >> Mitsubishi >> 2017 >> Lancer SE >> Repair and Diagnosis >> External Pages >> Different car >> Section 43 (Heating, Air Conditioning & Ventilation - With Diagnostics - Lancer) >> Manual A/C Diagnosis >> Symptom Procedures (Vehicles With A/C) >> INSPECTION PROCEDURE 2: Malfunction of the A/C controller assembly (A/C-ECU) Power Supply System >> Diagnosis

INSPECTION PROCEDURE 2: Malfunction of the A/C controller assembly (A/C-ECU) Power Supply System: Diagnosis

WARNING: This page is about a different car, the 2015 Mitsubishi Lancer. However, it is still accessible from the selected car via links, so may be relevant.

Required Special Tool: 

  1. STEP 1. Check A/C controller assembly (A/C-ECU) connector C-20 for loose, corroded or damaged terminals, or terminals pushed back in the connector  .

    Q: Is A/C-ECU connector C-20 in good condition? 

  2. STEP 2. Measure the voltage at A/C controller assembly (A/C-ECU) connector C-146  .
    1. Disconnect A/C controller assembly (A/C-ECU) connector C-146 and measure the voltage at the harness side.
    2. Turn the ignition switch to the "ON" position.
    3. Measure the voltage between terminal 20 and ground.
      • The measured value should be approximately 12 volts (battery positive voltage).

    Q: Is the measured voltage approximately 12 volts? 

    • YES:  Go to  Step 5.
    • NO:  Go to Step 3.
      Fig 1: Measuring Voltage Between Terminal 20 And Ground
      G09631154Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
  3. STEP 3. Check ETACS-ECU connector C-317 for loose, corroded or damaged terminals, or terminals pushed back in the connector  .

    Q: Is ETACS-ECU connector C-317 in good condition? 

  4. STEP 4. Check the wiring harness between A/C controller assembly (A/C-ECU) connector C-146 (terminal 20) and ETACS-ECU connector C-317 (terminal 5)  .
    • Check the A/C controller assembly (A/C-ECU) power supply line for open circuit.
      NOTE: Also check joint connector C-03 for loose, corroded, or damaged terminals, or terminals pushed back in the connector. If joint connector C-03 is damaged, repair or replace the connector as described in HARNESS CONNECTOR INSPECTION .

    Q: Is the wiring harness between A/C controller assembly (A/C-ECU) connector C-146 (terminal 20) and ETACS-ECU connector C-317 (terminal 5) in good condition? 

  5. STEP 5. Measure the voltage at A/C controller assembly (A/C-ECU) connector C-146  .
    1. Disconnect A/C controller assembly (A/C-ECU) connector C-146 and measure the voltage at the harness side.
    2. Measure the voltage between terminal 10 and ground.
      • The measured value should be approximately 12 volts (battery positive voltage).

    Q: Is the measured voltage approximately 12 V? 

    • YES:  Go to  Step 7.
    • NO:  Go to Step 6.
      Fig 2: Measuring Voltage Between Terminal 10 And Ground
      G09631155Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
  6. STEP 6. Check the wiring harness between A/C controller assembly (A/C-ECU) connector C-146 (terminal 10) and the fusible link (36)  .
    NOTE: Also check ETACS-ECU connectors C-307 and C-317 for loose, corroded, or damaged terminals, or terminals pushed back in the connector. If ETACS-ECU connectors C-307 and C-317 is damaged, repair or replace the connector as described in HARNESS CONNECTOR INSPECTION .
    • Check the A/C controller assembly (A/C-ECU) power supply line for open circuit.

    Q: Is the wiring harness between A/C controller assembly (A/C-ECU) connector C-146 (terminal 10) and the fusible link (36) in good condition? 

  7. STEP 7. Measure the resistance at A/C controller assembly (A/C-ECU) connector C-146  .
    1. Disconnect A/C controller assembly (A/C-ECU) connector C-146, and measure at the wiring harness side.
    2. Measure the resistance between terminal 9 and ground.
      • The measured value should be 2 ohms or less.

    Q: Does the measured resistance value correspond with this range? 

    • YES:  Replace the A/C controller assembly (A/C-ECU), and check that the A/C works normally.
    • NO:  Go to Step 8.
      Fig 3: Measuring Resistance Between Terminal 9 And Ground
      G09631156Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
  8. STEP 8. Check the wiring harness between A/C controller assembly (A/C-ECU) connector C-146 (terminal 9) and the ground  .
    • Check the A/C controller assembly (A/C-ECU) ground line for open circuit.

    Q: Is the wiring harness between A/C controller assembly (A/C-ECU) connector C-146 (terminal 9) and ground in good condition? 

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