Inspection Procedure 24: 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. 85) 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 CAUSE

Failed A/C compressor relay
Failed A/C compressor magnet clutch
Open/short circuit 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.

STEP 2. A/C compressor relay check.

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

Q. Is the check result normal?

	Go to Step 3 .

	Replace 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-06 engine-ECU connector

Q. Is the check result normal?

	Go to Step 5 .

	Repair or replace.

STEP 5. Perform voltage measurement at B-06 engine-ECU connector.

Disconnect connector, and measure at the harness side.
Voltage between terminal No. 85 and earth.

OK: System voltage

Q. Is the check result normal?

	Go to Step 6 .

	Check and repair harness between B-06 (terminal No. 85) 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.

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-06 (terminal No. 85) 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 connectors B-07, and repair if necessary.

Check output line for open/short circuit.

Q. Is the check result normal?

	Go to Step 9 .

	Repair.

STEP 9. Check harness between A-16X (terminal No. 1) A/C compressor relay connector and B-06 (terminal No. 85) 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.

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.

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.

STEP 12. Perform voltage measurement at B-06 engine-ECU connector.

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

A/C set temperature:

Voltage between terminal No. 85 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 ).