Inspection Procedure 6

Blower Air Volume cannot be Changed.

Blower Switch And Resistor Circuit:

TECHNICAL DESCRIPTION (COMMENT)
If the blower air amount can not be changed when the blower switch is operated, the blower switch may be defective.

TROUBLESHOOTING HINTS
- Malfunction of the resistor
- Malfunction of the blower switch
- The wiring harness or connectors may have loose, corroded, or damaged terminals, or terminals pushed back in the connector

DIAGNOSIS

Required Special Tools:
- MB991223: Test Harness Set

STEP 1. Check that the blower motor operates when the blower switch is moved to the "HI" position.

1. Turn the ignition switch to the "ON" position.
2. Turn the blower switch to the "HI" position.

Q: Does the blower motor operate when the blower switch is moved to the "HI" position?

YES: Go to STEP 4.

NO: Go to STEP 2.







STEP 2. Check blower switch connector C-125 and blower motor connector C-08 for loose, corroded or damaged terminals, or terminals pushed back in the connector.

Q: Are blower switch connector C-125 and blower motor connector C-08 in good condition?

YES: Go to Step 3.

NO: Repair or replace the connector. Refer to Harness Connector Inspection. The blower motor should operate normally.







STEP 3. Check the wiring harness between blower switch connector C-125 (terminal 6) and blower motor connector C-08 (terminal 1).

Q: Is the wiring harness between blower switch connector C-125 (terminal 6) and blower motor connector C-08 (terminal 1) in good condition?

YES: The blower motor should operate normally.

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







STEP 4. Check the resistor resistance value.

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

Q: Is the measured value at the standard value?

YES: Go to Step 5.

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







STEP 5. Check the blower switch continuity.

Follow the table to check the blower switch for continuity.

Q: Is the blower switch continuity in good condition?

YES: Go to Step 6.

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







STEP 6. Check blower switch connector C-125 and resistor connector C-09 for loose, corroded or damaged terminals, or terminals pushed back in the connector.

Q: Are blower switch connector C-125 and resistor connector C-09 in good condition?

YES: Go to Step 7.

NO: Repair or replace the connector. Refer to Harness Connector Inspection. The blower motor should operate normally.







STEP 7. Check the wiring harness between blower switch connector C-125 (terminals 1, 4 and 5) and resistor connector C-09 (terminals 4, 1 and 3).

Q: Is the wiring harness between blower switch connector C-125 (terminals 1, 4 and 5) and resistor connector C-09 (terminals 4,1 and 3) in good condition?

YES: Go to Step 8.

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




STEP 8. Check resistor connector C-09 and blower motor connector C-08 for loose, corroded or damaged terminals, or terminals pushed back in the connector.

Q: Are resistor connector C-09 and blower motor connector C-08 in good condition?

YES: Go to Step 9.

NO: Repair or replace the connector. Refer to Harness Connector Inspection. The blower motor should operate normally.




STEP 9. Check the wiring harness between blower motor connector C-08 (terminal 1) and resistor connector C-09 (terminal 2).

Q: Is the wiring harness between blower motor connector C-08 (terminal 1) and resistor connector C-09 (terminal 2) in good condition?

YES: It can be assumed that this malfunction is intermittent. Refer to How to Cope with intermittent Malfunctions.

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