Inspection Procedure 5

INSPECTION PROCEDURE 5: Blower Air Amount cannot be Changed.

Blower Motor Circuit Part 1:

Blower Motor Circuit Part 2:

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 A/C-ECU
- Damaged harness wires or connectors

DIAGNOSIS

Required Special Tools:
- MB991223: Harness Set
- MB992006: Extra Fine Probe

STEP 1. Check power transistor connector C-120 for loose, corroded or damaged terminals, or terminals pushed back in the connector.

Q: Is power transistor connector C-120 in good condition?

YES: Go to Step 2.

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

STEP 2. Measure the resistance at power transistor connector C-120.

1. Disconnect power transistor connector C-120, and measure the resistance at the wiring harness side.




2. Measure the resistance value between terminal 1 and ground.

OK: 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-120 (terminal 1) and ground.

Q: Is the wiring harness between power transistor connector C-120 (terminal 1) and ground 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. The blower motor should operate normally.

STEP 4. Check A/C-ECU connector C-109 for loose, corroded or damaged terminals, or terminals pushed back in the connector.

Q: Is A/C-ECU connector C-109 in good condition?

YES: Go to Step 5.

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

STEP 5. Check the wiring harness between A/C-ECU connector C-109 (terminals 1 and 2) and power transistor connector C-120 (terminals 2 and 4).

Q: Is the wiring harness between A/C-ECU connector C-109 (terminals 1 and 2) and power transistor connector C-120 (terminals 2 and 4) in good condition?

YES: Go to Step 6.

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

STEP 6. 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.