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
|
|
STEP 1. 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 2.
|
|
|
|
|
|
 Replace the A/C compressor relay.
|
|
|
|
|
|
STEP 2. Voltage measurement at A/C compressor relay connector (power supply line).
|
|
|
(1)Remove the relay, and measure at the relay box side.
|
|
|
(2)Check the voltage between the A/C compressor relay connector (power supply line) and body 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 to earth, and open circuit in power supply line between battery and A/C compressor relay connector.
|
|
|
|
|
|
STEP 3. Check of harness damage in power supply line between battery and A/C compressor relay connector.
|
|
|
Q.
Is the check result normal?
|
|
|
Go to Step 4.
|
|
|
|
|
|
Repair the connector(s) or wiring harness.
|
|
|
|
|
|
STEP 4. Voltage measurement at engine-ECU connector (AC/R terminal).
|
|
|
(1)Disconnect the connector, and measure at the wiring harness side.
|
|
|
(2)Check the voltage between the engine-ECU connector (AC/R terminal) and body earth.
OK: System voltage
|
|
|
Q.
Is the check result normal?
|
|
|
Go to Step 5.
|
|
|
|
|
|
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.
|
|
|
|
|
|
STEP 5. Check of harness damage in AC/R line between A/C compressor relay connector and engine-ECU connector.
|
|
|
Q.
Is the check result normal?
|
|
|
Go to Step 6.
|
|
|
|
|
|
Repair the connector(s) or wiring harness.
|
|
|
|
|
|
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.
|
|
|
Q.
Is the check result normal?
|
|
|
Go to Step 7.
|
|
|
|
|
|
Repair the connector(s) or wiring harness.
|
|
|
|
|
|
STEP 7. Check A/C compressor clutch operating conditions.
|
|
|
- Disconnect engine-ECU connector, and short-circuit engine-ECU connector (AC/R terminal) to the body earth.
|
|
|
OK: A/C compressor clutch operates.
|
|
|
Q.
Is the check result normal?
|
|
|
Replace the engine-ECU.
|
|
|
|
|
|
Replace the A/C compressor assembly.
|
|
|
|