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Inspection Procedure 28: A/C Compressor Relay System
 
 
 
 
CIRCUIT OPERATION
  • Battery voltage is applied to the A/C compressor relay.
  • ECM 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.
 
 
COMMENT
  • When the A/C switch ON signal is input into the ECM, the ECM 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.
 
 
TROUBLESHOOTING HINTS (The most likely causes for this case:)
  • 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 ECM
 
 
DIAGNOSIS
STEP 1. Check A/C compressor relay itself.
Check A/C compressor relay itself (Refer to GROUP 55A - On-vehicle Service - Relay Check ).
Is the A/C compressor relay condition normal?
Go to Step 2.
Replace the A/C compressor relay.
 
STEP 2. Measure the voltage at A/C compressor relay.
(1) Disconnect the connector and measure at relay box side.
(2) Turn the ignition switch to the "ON" position.
(3) Measure the voltage between terminal battery line and ground.
  • Voltage should be battery positive voltage.
(4) Turn the ignition switch to the "LOCK" (OFF) position.
Is battery positive voltage (approximately 12 volts) present?
Go to Step 3.
  • Repair or replace the connector(s), or check and repair the harness of short circuit to ground, and open circuit in power supply line between battery and A/C compressor relay connector.
 
STEP 3. Measure the voltage at A/C compressor relay connector.
(1) Disconnect the connector and measure at the harness side.
(2) Turn the ignition switch to the "ON" position.
(3) Measure the voltage between terminal IG2 line and ground.
  • Voltage should be battery positive voltage.
(4) Turn the ignition switch to the "LOCK" (OFF) position.
Is battery positive voltage (approximately 12 volts) present?
<Vehicles without KOS> : Go to Step 4.
<Vehicles with KOS> : Go to Step 5.
<Vehicles without KOS> : Repair or replace the connector(s), or check and repair the harness of short circuit to ground, and open circuit in IG2 line between ignition switch and A/C compressor relay connector.
<Vehicles with KOS> : Repair or replace the connector(s), or check and repair the harness of short circuit to ground, 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.
Is the harness wire in good condition?
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.
Is the harness wire in good condition?
Go to Step 6.
Repair the connector(s) or wiring harness.
 
STEP 6. Measure the voltage at ECM connector.
(1) Disconnect the connector and measure at the harness side.
(2) Turn the ignition switch to the "ON" position.
(3) Measure the voltage between terminal AC/R line and ground.
  • Voltage should be battery positive voltage.
(4) Turn the ignition switch to the "LOCK" (OFF) position.
Is battery positive voltage (approximately 12 volts) present?
Go to Step 7.
  • Repair or replace the connector(s), or check and repair the harness of short circuit to ground, and open circuit in AC/R line between A/C compressor relay connector and ECM connector.
 
STEP 7. Check of damage in AC/R line between A/C compressor relay connector and ECM connector.
Is the harness wire in good condition?
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.
Is the harness wire in good condition?
Go to Step 9.
Repair the connector(s) or wiring harness.
 
STEP 9. Check A/C compressor clutch operating conditions.
Disconnect ECM connector, and short-circuit harness side terminal AC/R to the ground.
  • A/C compressor clutch operates.
Is the actuator operating properly?
Replace the ECM.
Replace the A/C compressor assembly.