INSPECTION PROCEDURE 5: Blower Air Amount cannot be Changed: Diagnosis

Required Special Tools: 

• MB991223: Harness Set
• MB992006: Extra Fine Probe

1. STEP 1. 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 2.
   • NO:  Repair or replace the connector. Refer to HARNESS CONNECTOR INSPECTION . The blower motor should operate normally.
2. STEP 2. 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  4.
      • NO:  Go to Step 3.
        Fig 1: Measuring Resistance Value Between Terminal 1 And Ground

        Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
3. STEP 3. 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.
4. STEP 4. 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 5.
   • NO:  Repair or replace the connector. Refer to HARNESS CONNECTOR INSPECTION . The blower motor should operate normally.
5. STEP 5. 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 6.
     • NO:  Repair the wiring harness. The blower motor should operate normally.
6. STEP 6. 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.