Inspection Procedure 21: A/C Compressor Relay System
OPERATION
- Battery voltage is applied to the A/C compressor relay connector terminals.
- 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 connector terminal to the A/C compressor connector terminal.
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 and the magnet latch actuates.
PROBABLE CAUSES
- Failed A/C compressor relay
- Failed A/C compressor
- Open/short circuit or damage in the A/C compressor relay circuit or loose connector contact.
- Failed engine-ECU
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STEP 1. Check A/C compressor relay itself.
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- Check A/C compressor relay itself (Refer to GROUP 55 - On-vehicle Service - Relay Check
).
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Q.
Is the check result normal?
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Go to Step 2.
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Replace the A/C compressor relay.
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STEP 2. Voltage measurement at A/C compressor relay connector (power supply line).
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(1)Remove the relay, and measure at the relay box side.
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(2)Check the voltage between the A/C compressor relay connector (power supply line) and body earth. OK: System voltage
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Q.
Is the check result normal?
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Go to Step 3.
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![](../../../buttons/03btn002.png)
Repair or replace the connector(s), or check and repair the harness of short to earth, and open circuit in power supply line between battery and A/C compressor relay connector.
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STEP 3. Check of harness damage in power supply line between battery and A/C compressor relay connector.
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Q.
Is the check result normal?
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Go to Step 4.
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Repair the connector(s) or wiring harness.
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STEP 4. Voltage measurement at engine-ECU connector (AC/R terminal).
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(1)Disconnect the connector, and measure at the wiring harness side.
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(2)Check the voltage between the engine-ECU connector (AC/R terminal) and body earth. OK: System voltage
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Q.
Is the check result normal?
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Go to Step 5.
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![](../../../buttons/03btn002.png)
Repair or replace the connector(s), or check and repair the harness of short to earth, and open circuit in AC/R line between A/C compressor relay connector and engine-ECU connector.
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STEP 5. Check of harness damage in AC/R line between A/C compressor relay connector and engine-ECU connector.
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Q.
Is the check result normal?
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Go to Step 6.
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Repair the connector(s) or wiring harness.
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STEP 6. Check of short to earth, open circuit and damage in power supply line between A/C compressor relay connector and A/C compressor connector.
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Q.
Is the check result normal?
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Go to Step 7.
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Repair the connector(s) or wiring harness.
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STEP 7. Check A/C compressor clutch operating conditions.
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- Disconnect engine-ECU connector, and short-circuit engine-ECU connector (AC/R terminal) to the body earth.
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OK: A/C compressor clutch operates.
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Q.
Is the check result normal?
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Replace the engine-ECU.
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Replace the A/C compressor assembly.
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