Inspection Procedure 21: A/C Compressor Relay System


OPERATION



  • Battery voltage is applied to the A/C compressor relay (terminal No. 2 and No. 4).
  • Engine-ECU (terminal No. 102) applies current to the A/C compressor relay coil by turning ON the power transistor in the unit in order to turn the relay ON.
  • When the A/C compressor relay turns ON, battery voltage is supplied by the A/C compressor relay (terminal No. 3) to the A/C compressor (terminal No. 1).

FUNCTION



  • When the A/C switch ON signal is input into the engine-ECU, the engine-ECU turns ON the A/C compressor relay. This causes battery voltage to be supplied to the A/C compressor assembly and the A/C compressor clutch actuates.

PROBABLE CAUSES



  • Failed A/C compressor relay
  • Failed A/C compressor assembly
  • 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-20X A/C compressor relay connector

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

STEP 2. Check A/C compressor relay itself.

  • Check A/C compressor relay itself (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-20X A/C compressor relay.

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

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

    Check and repair harness between battery and A-20X (terminal No. 2 and No. 4) A/C compressor relay connector.

    • Check power supply line for open/short circuit.

STEP 4. Check harness between battery and A-20X (terminal No. 2 and No. 4) A/C compressor relay connector.

  • Check power supply line for damage.

Q. Is the check result normal?
Go to Step 5 .
Repair the damaged harness wire.

STEP 5. Connector check: B-27 engine-ECU connector

Q. Is the check result normal?
Go to Step 6 .
Repair or replace the connector.

STEP 6. Perform voltage measurement at B-27 engine-ECU connector.

  • Disconnect connector, and measure at harness side.
  • Voltage between terminal No. 102 and earth.
OK: System voltage

Q. Is the check result normal?
Go to Step 7 .

    Check and repair harness between A-20X (terminal No. 1) A/C compressor relay connector and B-27 (terminal No. 102) engine-ECU connector.

    • Check signal line for open/short circuit.

STEP 7. Check harness between A-20X (terminal No. 1) A/C compressor relay connector and B-27 (terminal No. 102) engine-ECU connector.

  • Check signal line for damage.

Q. Is the check result normal?
Go to Step 8 .
Repair the damaged harness wire.

STEP 8. Connector check: B-115 A/C compressor assembly connector


Q. Is the check result normal?
Go to Step 9 .
Repair or replace the connector.

STEP 9. Check harness between A-20X (terminal No. 3) A/C compressor relay connector and B-115 (terminal No. 1) A/C compressor assembly connector.
note Before checking harness, check intermediate connector A-17, and repair if necessary.

  • Check power supply line for open/short circuit and damage.

Q. Is the check result normal?
Go to Step 10 .
Repair the damaged harness wire.

STEP 10. Check A/C compressor clutch operating conditions.

  • Disconnect B-27 engine-ECU connector, and short-circuit terminal No. 102 to the earth.
OK: A/C compressor clutch operates.

Q. Is the check result normal?
Replace the engine-ECU.
Replace the A/C compressor assembly.