Inspection Procedure 25: 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. 3) from the ignition switch. The engine-A/T-ECU (terminal No. 8) 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 relay is in ON position, the battery voltage is supplied to the A/C compressor (terminal No. 1) from the A/C compressor relay (terminal No. 1).

FUNCTION

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

PROBABLE CAUSE

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

DIAGNOSIS PROCEDURE

STEP 1. Connector check: B-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 ).

Q. Is the check result normal?

	Go to Step 3 .

	Replace A/C compressor relay.

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

Remove relay, and measure at relay box side.
Ignition switch: ON
Voltage between terminal No. 3 and earth.

OK: System voltage

Q. Is the check result normal?

Go to Step 5 .

Go to Step 4 .

STEP 4. Connector check: C-307 ignition switch connector

Q. Is the check result normal?

Check power supply line for open/short circuit.

Repair or replace.

STEP 5. Perform voltage measurement at B-16X A/C compressor relay connector.

Remove relay, and measure at relay box side.
Voltage between terminal No. 4 and earth.

OK: System voltage

Q. Is the check result normal?

Go to Step 6 .

Check power supply line for open/short circuit.

STEP 6. Connector check: B-120 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-120 A/C compressor assembly connector.

Disconnect connector, and measure at harness side.
Remove B-16X (terminal No. 1 and No. 4) A/C compressor relay and short-circuit of harness side connector.
Voltage between terminal No. 1 and earth.

OK: System voltage

Q. Is the check result normal?

Go to Step 8 .

Check power supply line for open/short circuit.

STEP 8. Connector check: C-110 engine-A/T-ECU connector

Q. Is the check result normal?

Go to Step 9 .

Repair or replace.

STEP 9. Perform voltage measurement at C-110 engine-A/T-ECU connector.

Disconnect connector, and measure at harness side.
Ignition switch: ON
Voltage between terminal No. 8 and earth.

OK: System voltage

Q. Is the check result normal?

Go to Step 12 .

Go to Step 10 .

STEP 10. Check harness between B-16X (terminal No. 2) A/C compressor relay connector and C-110 (terminal No. 8) engine-A/T-ECU connector.

Check earthing line for open/short circuit.

Q. Is the check result normal?

Go to Step 11 .

Repair.

STEP 11. M.U.T.-III data list

Item 49: A/C relay

Engine: Idling
A/C set temperature:

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 ).

	Replace engine-A/T-ECU.

STEP 12. Check harness between B-16X (terminal No. 2) A/C compressor relay connector and C-110 (terminal No. 8) engine-A/T-ECU connector.

Check earthing line for damage.

Q. Is the check result normal?

Go to Step 13 .

Repair.

STEP 13. Connector check: C-307 ignition switch connector

Q. Is the check result normal?

Go to Step 14 .

Repair or replace.

STEP 14. Check harness between C-307 (terminal No. 4) ignition switch connector and B-16X (terminal No. 3) A/C compressor relay connector.

note

Before checking harness, check intermediate connectors C-17, C-205,and C-202 and repair if necessary.

Check power supply line for damage.

Q. Is the check result normal?

Go to Step 15 .

Repair.

STEP 15. Check harness between battery and B-16X (terminal No. 4) A/C compressor relay connector.

note

Before checking harness, check intermediate connector A-16, and repair if necessary.

Check power supply line for damage.

Q. Is the check result normal?

Go to Step 16 .

Repair.

STEP 16. Check harness between B-16X (terminal No. 1) A/C compressor relay connector and B-120 (terminal No. 1) A/C compressor assembly connector.

Check power supply line for damage.

Q. Is the check result normal?

Replace A/C compressor magnetic clutch.

Repair.