INSPECTION PROCEDURE 4: The blower air volume cannot be changed

COMMENTS ON TROUBLE SYMPTOM

If air volume cannot be adjusted by using the blower control, the A/C control panel, the auto A/C controller assembly (A/C-ECU) or the power transistor may be faulty.

PROBABLE CAUSES

Malfunction of the A/C control panel
Malfunction of the power transistor
Damaged wiring harness or connectors
Malfunction of the auto A/C controller assembly (A/C-ECU)

DIAGNOSIS PROCEDURE

STEP 1. M.U.T.-III CAN bus diagnostics

Use the M.U.T.-III to diagnose the CAN bus lines.

Q. Is the check result normal?

	Go to Step 2.

	Repair the CAN bus lines (Refer to GROUP 54C, Troubleshooting ).

STEP 2. M.U.T.-III diagnosis code

Check that the diagnosis code related to the air conditioner is not set.

Q. Is the diagnosis code set?

	Carry out the diagnosis code procedures. Refer to .

	Go to Step 3.

STEP 3. Resistance measurement at the power transistor connector.

(1)Disconnect the connector, and measure at the wiring harness side.

(2)Continuity between terminal 2 and body earth
OK: Continuity exists (2 Ω or less)

Q. Is the check result normal?

	Go to Step 4.

	Repair the wiring harness wires between power transistor connector terminal No. 1 and body earth.

STEP 4. Check open circuit in RVM, BASE and E line between power transistor, body earth and auto A/C controller assembly (A/C-ECU)

Q. Is the check result normal?

	Go to Step 5.

	Repair the connector(s) or wiring harness.

STEP 5. Check the data list below on the M.U.T.-III.

All the following items in the data list should be normal.

Item No.68:Front blower fan

Q. Is the check result normal?

	Go to Step 6.

	Replace the auto A/C controller assembly (A/C-ECU).

STEP 6. Replace the power transistor and check the trouble symptom

Check that the blower motor operates normally.

Q. Does the blower motor work normally?

	This diagnosis is complete.

	Replace the auto A/C controller assembly (A/C-ECU).