Inspection Procedure 5

INSPECTION PROCEDURE 5: Blower Air Amount cannot be Changed.










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-119 for loose, corroded or damaged terminals, or terminals pushed back in the connector.

Q. Is power transistor connector C-119 in good condition?

YES Go to Step 2.
NO Repair or replace the connector. Harness Connector Inspection.The blower motor should operate normally.
STEP 2. Measure the resistance at power transistor connector C-119.

(1)Disconnect power transistor connector C-119, 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-119 (terminal 1) and ground.

- Check the power transistor ground line for open circuit.

Q. Is the wiring harness between power transistor connector C-119 (terminal 1) 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. The blower motor should operate normally.
STEP 4. Check A/C-ECU connector C-22 for loose, corroded or damaged terminals, or terminals pushed back in the connector.

Q. Is A/C-ECU connector C-22 in good condition?

YES Go to Step 5.
NO Repair or replace the connector. Harness Connector Inspection.The blower motor should operate normally.
STEP 5. Check the wiring harness between A/C-ECU connector C-22 (terminals 1 and 2) and power transistor connector C-119 (terminals 2 and 4).

- Check the A/C-ECU signal line for open and short circuit.

Q. Is the wiring harness between A/C-ECU connector C-22 (terminals 1 and 2) and power transistor connector C-119 (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.