Inspection Procedure 4

INSPECTION PROCEDURE 4: Blower Fan and Motor do not Turn.

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 open/damaged/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 Tools:

- MB991223: Harness Set
- MB992006: Extra Fine Probe
- MB991958: Scan Tool (M.U.T.-III Sub Assembly)
- MB991824: V.C.I.
- MB991827: M.U.T.-III USB Cable
- MB991910: M.U.T.-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 Automatic Air Conditioning.

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. How to Cope With Intermittent Malfunctions.
NO Replace the A/C-ECU.
STEP 4. Check the blower relay continuity.

Follow the table below 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. 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 motor.

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. Harness Connector Inspection.

STEP 8. Check the wiring harness for open circuit.

(1)Disconnect A/C-ECU connector C-15 and power transistor connector C-107, and measure the resistance at the wiring harness side.

(2)Measure the resistance between A/C-ECU connector C-15 terminal 17 and power transistor connector C-107 terminal 1.
OK: Less than 2 ohms

Q. Is the check result normal?

YES Go to Step 10.

NO Go to Step 9.

STEP 9. Check the wiring harness between A/C-ECU connector C-15 (terminal 17) and power transistor connector C-107 (terminal 1).

Q. Is the wiring harness between A/C-ECU connector C-15 (terminal 17) and power transistor connector C-107 (terminal 1) in good condition?

YES It can be assumed that this malfunction is intermittent. How to Cope With Intermittent Malfunctions.

NO Repair the wiring harness.

STEP 10. Check the wiring harness for open circuit.

(1)Disconnect A/C-ECU connector C-15 and power transistor connector C-107, and measure the resistance at the wiring harness side.

(2)Measure the resistance between A/C-ECU connector C-15 terminal 18 and power transistor connector C-107 terminal 3.
OK: Less than 2 ohms

Q. Is the check result normal?

YES Go to Step 12.

NO Go to Step 11.

STEP 11. Check the wiring harness between A/C-ECU connector C-15 (terminal 18) and power transistor connector C-107 (terminal 3).

(1)Disconnect power transistor connector C-107, and measure the resistance at the wiring harness side.

(2)Measure the resistance between power transistor connector C-107 terminal 2 and ground.
OK: Less than 2 ohms

Q. Is the check result normal?

YES Go to Step 14.

NO Go to Step 13.

STEP 13. Check the wiring harness between power transistor connector C-107 (terminal 2) and ground.

Q. Is the wiring harness between power transistor connector C-107 (terminal 2) and ground in good condition?

YES It can be assumed that this malfunction is intermittent. How to Cope With Intermittent Malfunctions.

NO Repair the wiring harness.

STEP 14. 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: Less than 2 ohms

Q. Is the check result normal?

YES Go to Step 16.

NO Go to Step 15.

STEP 15. 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. How to Cope With Intermittent Malfunctions.

NO Repair the wiring harness.

STEP 16. Check the wiring harness for open circuit.

(1)Disconnect blower motor connector C-116 and junction block connector C-202, and measure the resistance at the wiring harness side.

(2)Measure the resistance between blower motor connector C-116 terminal 1 and junction block connector C-202 terminal 3.
OK: Less than 2 ohms

Q. Is the check result normal?

YES Go to Step 18.

NO Go to Step 17.

STEP 17. Check the wiring harness between blower motor connector C-116 (terminal 1) and junction block connector C-202 (terminal 3).

Q. Is the wiring harness between blower motor connector C-116 (terminal 1) and junction block connector C-202 (terminal 3) in good condition?

YES It can be assumed that this malfunction is intermittent. How to Cope With Intermittent Malfunctions.

NO Repair the wiring harness.

STEP 18. Measure the resistance at A/C-ECU connector C-15.

(1)Disconnect A/C-ECU connector C-15, and measure the resistance at the wiring harness side.

(2)Measure the resistance value between terminal 17 and ground.
OK: 1 kohms or more

Q. Does the measured resistance value correspond with this range?

YES Go to Step 20.

NO Go to Step 19.

STEP 19. Check the wiring harness between A/C-ECU connector C-15 (terminal 17) and power transistor connector C-107 (terminal 1).

(1)Disconnect A/C-ECU connector C-15, and measure the resistance at the wiring harness side.

(2)Measure the resistance value between terminal 18 and ground.
OK: 1 kohms or more

Q. Does the measured resistance value correspond with this range?

YES Go to Step 22.

NO Go to Step 21.

STEP 21. Check the wiring harness between A/C-ECU connector C-15 (terminal 18) and power transistor connector C-107 (terminal 3).

Q. Is the wiring harness between A/C-ECU connector C-15 (terminal 18) and power transistor connector C-107 (terminal 3) in good condition?

YES It can be assumed that this malfunction is intermittent. How to Cope With Intermittent Malfunctions.

NO Repair the wiring harness.

STEP 22. 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.