Inspection Procedure 26: A/C Compressor Relay System










OPERATION



  • The battery voltage is applied to the A/C compressor relay (terminal No. 4).
  • The battery voltage is applied to the A/C compressor relay (terminal No. 2). The engine-ECU (terminal No. 41) makes the power transistor in the unit be in ON position and makes currents go on the A/C compressor relay coil, and that makes the relay be in ON position.
  • When the A/C compressor is in ON position, the battery voltage is supplied to the A/C compressor (terminal No. 1) from the A/C compressor relay assembly (terminal No. 3).

FUNCTION



  • When the A/C switch ON signal is input to the engine-ECU, the engine-ECU places the A/C compressor relay in the ON position. Accordingly, the battery voltage supplied to the A/C compressor operates the magnet clutch.

PROBABLE CAUSES



  • Failed A/C compressor relay
  • Failed A/C compressor clutch
  • Open/short circuit or harness damage in A/C compressor relay circuit or loose connector contact
  • Failed engine-ECU

DIAGNOSIS PROCEDURE

STEP 1. Connector check: A-16X A/C compressor relay connector

Q. Is the check result normal?
Go to Step 2 .
Repair or replace the connector.

STEP 2. A/C compressor relay check.

  • Check A/C compressor relay (Refer to GROUP 55 - On-vehicle Service - Relay Check ).

Q. Is the check result normal?
Go to Step 3 .
Replace the A/C compressor relay.

STEP 3. Perform voltage measurement at A-16X A/C compressor relay connector.

  • Remove relay, and measure at the relay box side.
  • Voltage between terminal No. 2 and earth, also between terminal No. 4 and earth.
OK: System voltage

Q. Is the check result normal?
Go to Step 4 .

    Check and repair harness between A-16X (terminal No. 2 and terminal No. 4) A/C compressor relay connector and battery.

    • Check power supply line for open/short circuit.

STEP 4. Connector check: B-18 engine-ECU connector

Q. Is the check result normal?
Go to Step 5 .
Repair or replace the connector.

STEP 5. Perform voltage measurement at B-18 engine-ECU connector.

  • Disconnect connector, and measure at the harness side.
  • Voltage between terminal No. 41 and earth.
OK: System voltage

Q. Is the check result normal?
Go to Step 6 .

    Check and repair harness between B-18 (terminal No. 41) engine-ECU connector and A-16X (terminal No. 1) A/C compressor relay connector.

    • Check earthing line for open/short circuit

STEP 6. Connector check: B-12 A/C compressor assembly connector

Q. Is the check result normal?
Go to Step 7 .
Repair or replace the connector.

STEP 7. Perform voltage measurement at B-12 A/C compressor assembly connector.

  • Disconnect connector, and measure at the harness side.
  • Using a jumper wire, connect B-18 (terminal No. 41) engine-ECU connector and earth.
  • Voltage between terminal No. 1 and earth.
OK: System voltage

Q. Is the check result normal?
Go to Step 10 .
Go to Step 8 .

STEP 8. Check harness between A-16X (terminal No. 3) A/C compressor relay connector and B-12 (terminal No. 1) A/C compressor assembly connector.
note Before checking harness, check intermediate connector B-07, and repair if necessary.

  • Check output line for open/short circuit.

Q. Is the check result normal?
Go to Step 9 .
Repair the damaged harness wire.

STEP 9. Check harness between A-16X (terminal No. 1) A/C compressor relay connector and B-18 (terminal No. 41) engine-ECU connector.

  • Check earthing line for damage.

Q. Is the check result normal?

    Check and repair harness between A-16X (terminal No. 2) A/C compressor relay connector and battery.

    • Check power supply line for damage.
Repair the damaged harness wire.

STEP 10. Check harness between battery and A-16X (terminal No. 4) A/C compressor relay connector.

  • Check power supply line for damage.

Q. Is the check result normal?
Go to Step 11 .
Repair the damaged harness wire.

STEP 11. Check harness between A-16X (terminal No. 3) A/C compressor relay connector and B-12 (terminal No. 1) A/C compressor assembly connector.
note Before checking harness, check intermediate connector B-07, and repair if necessary.

  • Check output line for damage.

Q. Is the check result normal?
Go to Step 12 .
Repair the damaged harness wire.

STEP 12. Perform voltage measurement at B-18 engine-ECU connector.

  • Measure engine-ECU terminal voltage.
  • Engine: Running at idle

  • 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. 41 and earth.
OK:
    1.0 V or less (when A/C is ON)
    System voltage (when A/C is OFF)

Q. Is the check result normal?
Go to Step 13 .
Replace the engine-ECU.

STEP 13. Check the trouble symptoms.

Q. Does trouble symptom persist?

Replace the A/C compressor assembly.
Intermittent malfunction (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunctions ).