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

MB991223: Harness Set
MB992006: Extra Fine Probe

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.
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.
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.
STEP 4. Check the wiring harness between blower motor connector C-113 (terminal 2) and power transistor connector C-112 (terminal 2).
- Check the power transistor signal line for open and short circuit.
Q: Is the wiring harness between blower motor connector C-113 (terminal 2) and power transistor connector C-112 (terminals 2) in good condition?
- YES: Go to Step 5.
- NO: Repair the wiring harness. The blower motor should operate normally.
STEP 5. Check A/C controller assembly (A/C-ECU) connector C-146 for loose, corroded or damaged terminals, or terminals pushed back in the connector.
Q: Is A/C controller assembly (A/C-ECU) connector C-146 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.
STEP 6. Check the wiring harness between A/C controller assembly (A/C-ECU) connector C-146 (terminal 15) and power transistor connector C-112 (terminal 4).
- Check the A/C controller assembly (A/C-ECU) signal line for open and short circuit.
Q: Is the wiring harness between A/C controller assembly (A/C-ECU) connector C-146 (terminal 15) and power transistor connector C-112 (terminal 4) in good condition?
- YES: Go to Step 7.
- NO: Repair the wiring harness. The blower motor should operate normally.
STEP 7. 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 controller assembly (A/C-ECU).