Inspection Procedure 5

INSPECTION PROCEDURE 5: Blower Fan and Motor does not Stop Turning.

Blower Motor Circuit:

FUNCTION
The air from the blower fan is cooled or warmed to control the temperature.

TROUBLESHOOTING HINTS
- Malfunction of connector.
- Malfunction of the harness (Blower motor circuit is shorted to ground)
- Malfunction of the blower motor
- Malfunction of the blower relay
- Malfunction of the power transistor
- Malfunction of the A/C-ECU

DIAGNOSIS

Required Special Tool:
- MB991223: Harness Set
- MB992006: Extra Fine Probe
- MB991958: Scan Tool (MUT-III Sub Assembly)
- MB991824: 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 P.55B-9.

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: 8 step
- Item 03: Blower fan: 16 step
- Check that the blower motor operates.

4. Turn the ignition switch to the "LOCK" (OFF) position.

Q: Does the motor operate normally?

YES: Go to Step 4.

NO: Go to Step 3.

STEP 3. Retest the system

Check the trouble symptom again.

Q: Is the check result satisfactory?

YES: It can be assumed that this malfunction is intermittent. Refer to How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunctions.

NO: Replace the A/C-ECU.

STEP 4. Check the blower relay continuity.







Follow the table to check the blower relay for continuity.

Q: Is the blower relay continuity in good condition?

YES: Go to Step 5.

NO: Replace the blower relay.




STEP 5. Check blower motor connector C-116 for loose, corroded or damaged terminals, or terminals pushed back in the connector.

Q: Is blower motor connector C-116 in good condition?

YES: Go to Step 6.

NO: Repair or replace the connector. Refer to Harness Connector Inspection.

STEP 6. Check the blower fan and motor operation.




When battery voltage is applied between the terminals, check that the motor operates. Also, check that there is no abnormal noise.

Q: Is there any abnormal noise?

YES: Go to Step 7.

NO: Replace the blower relay.




STEP 7. Check A/C-ECU connector C-15 and power transistor connector C-107 for loose, corroded or damaged terminals, or terminals pushed back in the connector.

Q: Are A/C-ECU connector C-15 and power transistor connector C-107 in good condition?

YES: Go to Step 8.

NO: Repair or replace the connector. Refer to Harness Connector Inspection.

STEP 8. Check the wiring harness for open circuit.




1. Disconnect blower motor connector C-116 and power transistor connector C-107, and measure the resistance at the wiring harness side.




2. Measure the resistance between blower motor connector C-116 terminal 2 and power transistor connector C-107 terminal 4.

OK: 1.5 ohm or more

Q: Is the check result normal?

YES: Go to Step 10.

NO: Go to Step 9.




STEP 9. Check the wiring harness between blower motor connector C-116 (terminal 2) and power transistor connector C-107 (terminal 4).

Q: Is the wiring harness between blower motor connector C-116 (terminal 2) and power transistor connector C-107 (terminal 4) in good condition?

YES: It can be assumed that this malfunction is intermittent. Refer to How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunctions.

NO: Repair the wiring harness.

STEP 10. 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.