Inspection Procedure 33

INSPECTION PROCEDURE 33: A/C system.

A/C Circuit:

COMMENT
- When the A/C is "ON" the ECM or the PCM turns "ON" the power transistor in the ECM or the PCM . The ECM or the PCM delays A/C engagement momentarily while it increases idle r/min. 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 operates.

TROUBLESHOOTING HINTS (The most likely causes for this case: )
- Malfunction of the A/C control system.
- Improper connector contact, open circuit or shorted harness wire.
- Malfunction of the ECM or the PCM .

DIAGNOSIS

STEP 1. Check harness connector B-20 at ECM or PCM for damage.

Q: Is the harness connector in good condition?

YES: Go to Step 2.

NO: Repair or replace it. Then confirm that the malfunction symptom is eliminated.

STEP 2. Check the circuit at ECM or PCM connector B-20.

1. Disconnect the connectors B-20 and measure at the harness side.
2. Turn the ignition switch to the "ON" position.

3. Measure the voltage between terminal No. 81 and ground.
- Voltage should be battery positive voltage.

4. Using a jumper wire, connect terminal No. 81 to ground.
- A/C compressor clutch relay should turn "ON".

5. Turn the ignition switch to the "LOCK" (OFF) position.

Q: Is the voltage and A/C compressor relay condition normal?

YES: Replace the ECM or the PCM. When the ECM or the PCM is replaced, register the encrypted code. Refer to Encrypted Code Registration Criteria Table in Antitheft and Alarm Systems. Then confirm that the malfunction symptom is eliminated.

NO: Refer to Manual A/C Diagnosis - Introduction To Heater, Air Conditioning And Ventilation Diagnosis . Automatic A/C Diagnosis - Introduction To Heater, Air Conditioning And Ventilation Diagnosis . Then confirm that the malfunction symptom is eliminated.