Inspection Procedure 33

A/C system.

A/C Circuit:

COMMENT
- When the A/C is "ON", the battery positive voltage is applied on the PCM (terminal No. 83) from the automatic compressor controller. When battery positive voltage is applied to the PCM, the PCM turns "ON" the power transistor in the PCM. 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 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 PCM.

DIAGNOSIS




STEP 1. Check connector C-110, C-112 at PCM for damage.

Q: Is the connector in good condition?

YES: Go to Step 2.

NO: Repair or replace it. Refer to Harness Connector Inspection. Then confirm that the malfunction symptom is eliminated.

STEP 2. Check the circuit at PCM connector C-112.




1. Disconnect the connector C-112 and measure at the harness side.
2. Turn the ignition switch to the "ON" position.




3. Measure the voltage between terminal No. 21 and ground.
- Voltage should measure battery positive voltage.

4. Using a jumper wire, connect terminal No. 21 to ground.
- A/C compressor relay should turn "ON".

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

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

YES: Go to Step 3.

NO: Refer to Heating and air conditioning - Introduction To Heater, Air Conditioning And Ventilation Diagnosis. Then confirm that the malfunction symptom is eliminated.

STEP 3. Check the circuit at PCM connector C-110.




1. Disconnect the connector C-110 and measure at the harness side.
2. Turn the ignition switch to the "ON" position.




3. Measure the voltage between terminal No. 83 and ground.
- Voltage should measure 1 volt or less when the A/C switch is "OFF".
- Voltage should measure battery positive voltage when thee A/C switch is "ON".

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

Q: Is the measured voltage within the specified range?

YES: Replace the PCM. Then confirm that the malfunction symptom is eliminated.

NO: Refer to Heating and air conditioning - Introduction To Heater, Air Conditioning And Ventilation Diagnosis.