Inspection Procedure 6

INSPECTION PROCEDURE 6: Blower Air Amount cannot be Changed.

Blower Switch And Resistor Circuit:

CIRCUIT OPERATION
If the front blower motor speed cannot be changed, the power transistor circuit is suspected.

TROUBLESHOOTING HINTS
- Malfunction of the power transistor
- Malfunction of the front A/C-ECU
- Damaged harness wires or connectors

DIAGNOSIS

Required Special Tool:
- MB991223: Test Harness Set
- MB992006: Extra Fine Probe

STEP 1. Check resistor connector C-127 for loose, corroded or damaged terminals, or terminals pushed back in the connector.






Q: Is resistor connector C-127 in good condition?

YES : Go to Step 2.

NO : Repair or replace the connector. Check that the A/C works normally.

STEP 2. Check the resistor resistance value.






Use an ohmmeter to measure the resistance between the terminals. Check that the measured value is at the standard value.






Q: Is the measured value at the standard value?

YES : Go to Step 3.

NO : Replace the resistor. The front blower motor should operate normally.

STEP 3. Check front blower motor connector C-111 for loose, corroded or damaged terminals, or terminals pushed back in the connector.






Q: Is front blower motor connector C-111 in good condition?

YES : Go to Step 4.

NO : Repair or replace the connector. Check that the A/C works normally.

STEP 4. Check the wiring harness front blower motor connector C-111 (terminal 1) and resistor connector C-127 (terminal 2).
- Check the front blower motor ground line for open circuit.






Q: Is the wiring harness between front blower motor connector C-111 (terminal 1) and resistor connector C-127 (terminal 2) in good condition?

YES : Go to Step 5.

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

STEP 5. Check blower switch connector C-41 for loose, corroded or damaged terminals, or terminals pushed back in the connector.






Q: Is blower switch connector C-41 in good condition?

YES : Go to Step 6.

NO : Repair or replace the connector. Check that the A/C works normally.

STEP 6. Check the blower switch continuity.






Follow the table below to check the blower switch for continuity.






Q: Is the blower switch continuity in good condition?

YES : Go to Step 7.

NO : Replace the blower switch. The front blower motor should operate normally.

STEP 7. Check the wiring harness blower switch connector C-41 (terminals 1, 6 and 2) and resistor connector C-127 (terminals 3,1 and 4).
- Check the blower switch ground line for open circuit.






Q: Are the wiring harness between blower switch connector C-41 (terminals 1, 6 and 2) and resistor connector C-127 (terminals 3,1 and 4) in good condition?

YES : It can be assumed that this malfunction is intermittent.

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