Inspection Procedure 34
A/C Circuit:
CIRCUIT OPERATION
- When the A/C is "ON," the battery positive voltage is applied on the ECM (terminal 83) PCM (terminal 83) from the A/C belt Lock-ECU.
When battery positive voltage is applied to the ECM or PCM, the ECM or PCM turns "ON" the power transistor in the ECM or PCM. The ECM or PCM delays A/C engagement momentarily while it increases idle rpm. Then the A/C compressor clutch relay coil will be energized.
With this, the A/C compressor clutch relay turns "ON," and the A/C compressor clutch functions.
TROUBLESHOOTING HINTS
The most likely causes for this case:
- Malfunction of the A/C control system.
- Malfunction of the A/C switch.
- Improper connector contact, open circuit or short-circuited harness wire.
- Malfunction of the ECM.
- Malfunction of the PCM.
DIAGNOSIS
STEP 1. Check circuit at ECM connector C-51, C-62
1. Disconnect connectors C-51, C-62
2. Turn the ignition switch to "ON" position.
3. Measure the voltage between terminal 20 and ground.
- Voltage should be battery positive voltage.
4. Measure the voltage between terminals 83 and ground.
- Voltage should be from 0 to 3 volts when the A/C switch is OFF.
- Voltage should be battery positive voltage when the A/C switch is ON.
5. Using a jumper wire, connector terminal 20 to the ground.
- A/C compressor should turn ON.
6. Turn the A/C switch OFF
7. Turn the ignition switch to "LOCK" (OFF) position.
If the checks above meet the specifications, go to Step 2.
If the checks above do not meet the specifications, check the A/C system. Refer to Heater, Air Conditioning and Ventilation Diagnosis.
Then check that the malfunction is eliminated.
STEP 2. Check harness connectors C-51, C-62 at the ECM
If harness connectors C-51, C-62
If harness connectors C-51, C-62
Refer to Harness Connector Inspection.
Then confirm that the malfunction is eliminated.