Inspection Procedure 8: heater switch system

COMMENTS ON TROUBLE SYMPTOM
If a heater switch signal is not set to the A/C-ECU, the heater switch or the heater switch circuit system may be defective.

PROBABLE CAUSES

  • Malfunction of the heater switch
  • Malfunction of the automatic A/C control panel (A/C-ECU)

DIAGNOSIS PROCEDURE

STEP 1. Connector check: C-151 heater switch connector

Q. Is the check result normal?

Go to Step 2.

Repair the connector.

STEP 2. Check the heater switch.
Refer to .

Q. Is the heater switch operating properly?
Go to Step 3.
Replace the heater switch.

STEP 3. Voltage measurement at C-151 heater switch connector.

(1)Disconnect the connector, and measure at the wiring harness side.
(2)Turn the ignition switch to the "ON" position.

(3)Voltage between terminal 2 and body earth.
OK: System voltage

Q. Is the check result normal?

Go to Step 5.

Go to Step 4.

STEP 4. Check the wiring harness between C-151 heater switch connector terminal No.2 and the ignition switch (IG2).



note Prior to the wiring harness inspection, check joint connector C-137, C-138, C-132, junction block connector C-209 and C-207, and repair if necessary.

  • Check the heater switch power supply line for open circuit.

Q. Is the check result normal?

The trouble can be an intermittent malfunction (Refer to GROUP 00, How to Cope with Intermittent Malfunction ).

Repair the wiring harness.

STEP 5. Connector check: C-105 engine-ECU connector

Q. Is the check result normal?

Go to Step 6.

Repair the connector.

STEP 6. Connector check: C-105 engine-ECU connector

Q. Is the check result normal?

Go to Step 7.

Repair the connector.

STEP 7. Check the wiring harness between C-151 heater switch connector terminal No.1 and C-105 engine-ECU connector terminal No.14.



  • Check the heater switch earth line for open circuit.

Q. Is the check result normal?

The trouble can be an intermittent malfunction (Refer to GROUP 00, How to Cope with Intermittent Malfunction .)

Repair the wiring harness.