Inspection Procedure 4: The Blower Air Volume cannot be Changed

COMMENTS ON TROUBLE SYMPTOM
If the blower air volume can not be changed when the blower switch is operated, the circuit between front power transistor and A/C-ECU may be defective.

PROBABLE CAUSES

  • Front power transistor
  • Damaged the wiring harness or connectors
  • Malfunction of the automatic air conditioner control panel (A/C-ECU)

DIAGNOSIS PROCEDURE

STEP 1. M.U.T.-III actuator test
Carry out the actuator test. (Refer to .)

  • Item 01, 02, 03: Blower motor

Q. Does the blower motor work normally?

Go to Step 2.
Go to Step 4.

STEP 2. M.U.T.-III data list
Check that the following service data display contents are normal. (Refer to .)

  • Item 20: Front blower fan
  • Item 21: Front blower fan (Target)

Q. Does the blower motor work normally?

Go to Step 3.
Go to Step 10.

STEP 3. Replace the front power transistor and check the trouble symptom
Check that the front blower motor operates normally.

Q. Does the blower motor work normally?

This diagnosis is complete.
Replace the automatic air conditioner control panel (A/C-ECU)

STEP 4. Connector check: C-12 front power transistor controller connector



Q. Is the check result normal?

Go to Step 5.

Repair the connector.

STEP 5. Resistance measurement at the C-12 front power transistor connector.



(1)Disconnect the connector, and measure at the wiring harness side.

(2)Continuity between terminal 2 and body earth
OK: 2Ω or less

Q. Is the check result normal?

Go to Step 7.

Go to Step 6.

STEP 6. Check the wiring harness between C-12 front power transistor connector terminal No.2 and body earth.




  • Check the blower linear controller earth line for open circuit.

Q. Is the check result normal?

The trouble can be an intermittent malfunction (Refer to GROUP 00, How to Cope with Intermittent Malfunction ).

Repair the wiring harness.

STEP 7. Connector check: C-106 A/C-ECU controller connector



Q. Is the check result normal?

Go to Step 8.

Repair the connector.

STEP 8. Check the wiring harness between C-106 A/C-ECU connector (terminals 2 and 3) and C-12 front power transistor controller connector (terminals 3 and 1).







  • Check the blower linear controller power supply line for open circuit.

Q. Is the check result normal?

Go to Step 9.

Repair the wiring harness.

STEP 9. Replace the front power transistor and check the trouble symptom
Check that the front blower motor operates normally.

Q. Does the blower motor work normally?

This diagnosis is complete.
Replace the automatic air conditioner control panel (A/C-ECU).

STEP 10. Check the trouble symptom
Check that the front blower motor operates normally.

Q. Is the check result normal?
This diagnosis is complete.
Replace the automatic air conditioner control panel (A/C-ECU).