Inspection Procedure 22: A/C Compressor Relay System

OPERATION

Battery voltage is applied to the A/C compressor relay.
Engine-ECU connector terminal AC/R 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 to the A/C compressor.

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. Check A/C compressor relay itself.

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

Q. Is the check result normal?

	Go to Step 2.

	Replace the A/C compressor relay.

STEP 2. Perform voltage measurement at A/C compressor relay.

Disconnect relay, and measure at relay box side.
Voltage between terminal battery line and earth.

OK: System voltage

Q. Is the check result normal?

	Go to Step 3.

	Repair or replace the connector(s), or check and repair the harness of short circuit to earth, and open circuit in power supply line between battery and A/C compressor relay connector.

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

Disconnect connector and measure at harness side.
Ignition switch: ON
Voltage between terminal IG2 line and earth.

OK: System voltage

Q. Is the check result normal?

	YES <Vehicles without KOS> : Go to Step 4.

	YES <Vehicles with KOS> : Go to Step 5.

	NO <Vehicles without KOS> : Repair or replace the connector(s), or check and repair the harness of short circuit to earth, and open circuit in IG2 line between ignition switch and A/C compressor relay connector.

	NO <Vehicles with KOS> : Repair or replace the connector(s), or check and repair the harness of short circuit to earth, and open circuit in IG2 line between IG2 relay and A/C compressor relay connector.

STEP 4. Check of damage in IG2 line between ignition switch connector and A/C compressor relay connector.

Q. Is the check result normal?

	Go to Step 6.

	Repair the connector(s) or wiring harness.

STEP 5. Check of damage in IG2 line between IG2 relay connector and A/C compressor relay connector.

Q. Is the check result normal?

	Go to Step 6.

	Repair the connector(s) or wiring harness.

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

Disconnect connector, and measure at harness side.
Voltage between terminal AC/R and earth.

OK: System voltage

Q. Is the check result normal?

	Go to Step 7.

	Repair or replace the connector(s), or check and repair the harness of short circuit to earth, and open circuit in AC/R line between A/C compressor relay connector and engine-ECU connector.

STEP 7. Check of damage in AC/R line between A/C compressor relay connector and engine-ECU connector.

Q. Is the check result normal?

	Go to Step 8.

	Repair the connector(s) or wiring harness.

STEP 8. Check of open circuit, short circuit, and damage in power supply line between A/C compressor relay connector and A/C compressor assembly connector.

Q. Is the check result normal?

	Go to Step 9.

	Repair the connector(s) or wiring harness.

STEP 9. Check A/C compressor clutch operating conditions.

Disconnect engine-ECU connector, and short-circuit harness side terminal AC/R 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.