Inspection Procedure 21: A/C switch system






OPERATION



  • The battery voltage is applied to the engine-A/T-ECU (terminal No. 69) from the A/C-ECU.

FUNCTION



  • When the A/C switch is in "ON" position, A/C switch ON signal is inputted to the engine-A/T-ECU from the A/C-ECU. In response to the signal, the engine-A/T-ECU controls the A/C compressor relay.

PROBABLE CAUSES



  • Failed A/C
  • Failed A/C system
  • Open/short circuit in A/C circuit or loose connector contact
  • Failed engine-A/T-ECU

DIAGNOSIS PROCEDURE

STEP 1. Perform voltage measurement at D-216 engine-A/T-ECU connector.

  • Measure engine-A/T-ECU terminal voltage.
  • Engine: Idling

  • A/C set temperature:

      • Maximum Cool when temperature in cabin is 25°C or more
      Maximum Hot when temperature in cabin is 25°C or less
  • Voltage between terminal No. 69 and earth.
OK:
    System voltage (when A/C is ON)
    0.5 V or less (when A/C is OFF)

Q. Is the check result normal?
Go to Step 2 .
Check A/C system (Refer to GROUP 55 - Troubleshooting - Check Chart for Trouble Symptoms ).

STEP 2. Connector check: D-216 engine-A/T-ECU connector

Q. Is the check result normal?
Go to Step 3 .
Repair or replace the connector.

STEP 3. M.U.T.-III data list

  • Item 76: A/C switch

  1. Engine: Idling
  2. A/C set temperature:

    Maximum Cool when temperature in cabin is 25°C or more
    Maximum Hot when temperature in cabin is 25°C or less
OK:
    ON (when A/C is ON)
    OFF (when A/C is OFF)

Q. Is the check result normal?
Intermittent malfunction (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunctions ).
Replace the engine-A/T-ECU.