Inspection Procedure 5

INSPECTION PROCEDURE 5: The Blower Air Volume cannot be Changed.

Blower Motor Circuit:

CIRCUIT OPERATION
If the blower air volume can not be changed when the blower switch is operated, the circuit between blower motor and A/C-ECU may be defective.

TROUBLESHOOTING HINTS
- Malfunction of the blower motor (blower linear controller).
- Damaged the wiring harness or connectors
- Malfunction of the A/C-ECU

DIAGNOSIS

Required Special Tools:
- MB991223: Harness Set
- MB992006: Extra Fine Probe
- MB991958: Scan Tool (MUT-III Sub Assembly)
- MB991824: Vehicle Communication Interface (V.C.I.)
- MB991827: MUT-III USB Cable
- MB991910: MUT-III Main Harness A

STEP 1. Using scan tool MB991958, read the diagnostic trouble code.

CAUTION: To prevent damage to scan tool MB991958, always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool MB991958.

Check if an A/C-ECU DTC is set.




1. Connect scan tool MB991958 to the data link connector.
2. Turn the ignition switch to the "ON" position.
3. Check if the DTC is set.
4. Turn the ignition switch to the "LOCK" (OFF) position.

Q: Is the check result satisfactory?

YES: Refer to Diagnostic Trouble Code Chart. Diagnostic Trouble Code Descriptions

NO: Go to Step 2.

STEP 2. Using scan tool MB991958, check actuator test.

1. Connect scan tool MB991958 to the data link connector.
2. Start the engine.
3. Use scan tool MB991958 to run the actuator test.
- Item 01: Blower fan: OFF
- Item 02: Blower fan: Low speed
- Item 03: Blower fan: Middle speed
- Item 04: Blower fan: High speed
- Check that the blower motor operates.
4. Turn the ignition switch to the "LOCK" (OFF) position.

Q: Does the motor operate normally?

YES: Replace the A/C-ECU.

NO: Go to Step 3.




STEP 3. Check the wiring harness between A/C-ECU connector C-25 (terminal 2) and blower linear controller connector C-31 (terminal 5).

Q: Is the wiring harness between A/C-ECU connector C-25 (terminal 2) and blower linear controller connector C-31 (terminal 5) in good condition?

YES: Replace the A/C-ECU or the blower linear controller.

NO: Repair the wiring harness. The blower motor should operate normally.