INSPECTION PROCEDURE 4: Blower Fan and Motor do not Turn: Diagnosis

Required Special Tools: 

• MB991223: Harness Set
• MB992006: Extra Fine Probe

1. STEP 1. Check blower motor connector C-113 for loose, corroded or damaged terminals, or terminals pushed back in the connector. 

   Q: Is blower motor connector C-113 in good condition? 

   • YES:  Go to Step 2.
   • NO:  Repair or replace the connector. Refer to HARNESS CONNECTOR INSPECTION . The blower motor should operate normally.
2. STEP 2. Measure the voltage at blower motor connector C-113. 
   1. Disconnect blower motor connector C-113, and measure the voltage at the wiring harness side.
   2. Turn the ignition switch to the "ON" position.
   3. Turn the blower switch to the "Maximum air volume" position.
   4. Measure the voltage between terminal 1 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 3.
        • NO:  Refer to INSPECTION PROCEDURE 10, "BLOWER MOTOR POWER SUPPLY SYSTEM  ."
          Fig 1: Measuring Voltage Between Terminal 1 And Ground

          Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
3. STEP 3. Check blower motor connector C-113 for loose, corroded or damaged terminals, or terminals pushed back in the connector. 

   Q: Is blower motor connector C-113 in good condition? 

   • YES:  Go to Step 4.
   • NO:  Repair or replace the connector. Refer to HARNESS CONNECTOR INSPECTION . The blower motor should operate normally.
4. STEP 4. Check the blower fan and motor operation. 

   Check that the motor turns when applying battery power between the connector terminals. Also check to see that there is no abnormal sound emitted from the motor at this time..

   Q: Is there any abnormal noise? 

   • YES:  Go to Step 5.
   • NO:  Replace the blower relay. The blower motor should operate normally.
     Fig 2: Applying Battery Power Between Connector Terminals

     Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
5. STEP 5. Check 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? 

   • YES:  Go to Step 6.
   • NO:  Repair or replace the connector. Refer to HARNESS CONNECTOR INSPECTION . The blower motor should operate normally.
6. STEP 6. Check the wiring harness between A/C-ECU connector C-20 (terminal 1) and blower motor connector C-113 (terminal 2). 
   • Check the AC-ECU signal line for open and short circuit.

     Q: Is the wiring harness between A/C-ECU connector C-20 (terminal 1) and blower motor connector C-113 (terminal 2) in good condition? 

     • YES:  Go to Step 7.
     • NO:  Repair the wiring harness. The blower motor should operate normally.
7. STEP 7. Check power transistor connector C-112 for loose, corroded or damaged terminals, or terminals pushed back in the connector. 

   Q: Is power transistor connector C-112 in good condition? 

   • YES:  Go to Step 8.
   • NO:  Repair or replace the connector. Refer to HARNESS CONNECTOR INSPECTION . The blower motor should operate normally.
8. STEP 8. Measure the resistance at power transistor connector C-112. 
   1. Disconnect power transistor connector C-112, and measure the resistance at the wiring harness side.
   2. Measure the resistance value between terminal 1 and ground.

      OK: The measured value should be 2 ohms or less 

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

      • YES:  Go to Step  10.
      • NO:  Go to Step 9.
        Fig 3: Measuring Resistance Value Between Terminal 1 And Ground

        Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
9. STEP 9. Check the wiring harness between power transistor connector C-112 (terminal 1) and ground. 
   • Check the power transistor ground line for open circuit.

     Q: Is the wiring harness between power transistor connector C-112 (terminal 1) and ground in good condition? 

     • YES:  It can be assumed that this malfunction is intermittent. Refer to HOW TO COPE WITH INTERMITTENT MALFUNCTIONS .
     • NO:  Repair the wiring harness. The blower motor should operate normally.
10. STEP 10. Check the wiring harness between A/C-ECU connector C-20 (terminals 1 and 2) and power transistor connector C-112 (terminals 2 and 4). 
    • Check the AC-ECU signal line for open and short circuit.

      Q: Is the wiring harness between A/C-ECU connector C-20 (terminals 1 and 2) and power transistor connector C-112 (terminals 2 and 4) in good condition? 

      • YES:  Go to Step 11.
      • NO:  Repair the wiring harness. The blower motor should operate normally.
11. STEP 11. Replace the power transistor and check the trouble symptom again 

    Check the trouble symptom again.

    Q: Is the check result satisfactory? 

    • YES:  The procedure is complete.
    • NO:  Replace the A/C-ECU.