Inspection Procedure 6

INSPECTION PROCEDURE 6: Front Blower Air Amount Cannot Be Changed.

Blower Motor Circuit:

CIRCUIT OPERATION
If the 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 Tools:
- MB991223: Harness Set
- MB992006: Extra Fine Probe

STEP 1. Check blower power transistor connector C-104 for loose, corroded or damaged terminals, or terminals pushed back in the connector.







Q: Is power transistor connector C-104 in good condition?

YES : Go to Step 2.

NO : Repair or replace the connector. The blower motor should operate normally.

STEP 2. Measure the resistance at power transistor connector C-104.







1. Disconnect power transistor connector C-104, and measure the resistance at the wiring harness side.







2. Measure the resistance value between terminal 2 and ground.
- The measured value should be 2 ohms or less.

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

YES : Go to Step 4.

NO : Go to Step 3.

STEP 3. Check the wiring harness between power transistor connector C-104 (terminal 2) and ground.







- Check the power transistor ground line for open circuit.

Q: Is the wiring harness between power transistor connector C-104 (terminal 2) and ground in good condition?

YES : The blower motor should operate normally.

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

STEP 4. Check blower motor connector C-115 for loose, corroded or damaged terminals, or terminals pushed back in the connector.







Q: Is blower motor connector C-115 in good condition?

YES : Go to Step 5.

NO : Repair or replace the connector. The blower motor should operate normally.

STEP 5. Check the wiring harness between power transistor connector C-104 (terminal 4) and blower motor connector C-115 (terminal 2).







- Check the blower motor ground line for open circuit.

Q: Is the wiring harness between power transistor connector C-104 (terminal 4) and blower motor connector C-115 (terminal 2) in good condition?

YES : Go to Step 6.

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

STEP 6. Check A/C-ECU connector C-15 for loose, corroded or damaged terminals, or terminals pushed back in the connector.







Q: Is A/C-ECU connector C-15 in good condition?

YES : Go to Step 7.

NO : Repair or replace the connector. The blower motor should operate normally.

STEP 7. Check the wiring harness between power transistor connector C-104 (terminals 1 and 3) and A/C-ECU connector C-15 (terminals 17 and 18).







- Check the blower motor ground line for open circuit.

Q: Are the wiring harness between power transistor connector C-104 (terminals 1 and 3) and A/C-ECU connector C-15 (terminals 17 and 18) in good condition?

YES : Go to Step 8.

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

STEP 8. Replace the power transistor.

Q: Does the blower motor operate normally?

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

NO : Replace the A/C-ECU. Check that the A/C works normally.