FULL-AUTO AIR CONDITIONER SYSTEM

id074000004000

Outline

• The front/rear climate control units perform the following controls based on the input signals from each dial/switch and each sensor.

― Airflow temperature control

― Airflow volume control

― Airflow mode control

― Air intake control

― A/C compressor control

― Air conditioner i-stop control (With i-stop)

Functions

• The front/rear climate control units perform each control of the full-auto air conditioning system based on the target temperature, the warm-up control judgment, and the windshield fogging judgment.

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Windshield fogging judgment (With humidity sensor)

• The front climate control unit perform the windshield fogging judgment based on the signal from the humidity sensor and applies the calculated correction value from the each signal.

• The front climate control unit dehumidifies the air around the windshield (interior) by changing the settings for each control (airflow mode control, air intake control, and A/C compressor control) according to the fogging level of the windshield to defog the windshield.

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Airflow temperature control

• The airflow temperature control operates the front/rear air mix actuator and switches the air mix door position in conjunction with the airflow temperature setting and the vehicle conditions.

Airflow volume control

• The airflow volume control changes the front/rear blower motor control speed and switches the airflow volume in conjunction with the target temperature, airflow volume setting, airflow temperature setting, airflow mode setting, and the vehicle conditions.

Airflow mode control

• The airflow mode control operates the front/rear airflow mode actuator and switches the position of the airflow mode door in conjunction with the target temperature, the airflow mode setting, and the vehicle conditions.

Air intake control

• The air intake control operates the air intake actuator and switches the air intake door position in conjunction with the air intake setting, airflow mode setting, and the vehicle conditions.

A/C compressor control

• The A/C compressor control sends the A/C signal to the PCM based on the front climate control unit operation and signals from each sensor.

Air conditioner i-stop control (With i-stop)

• The front climate control unit determines i-stop control (engine stop control) according to the operation condition of the air conditioner system and sends i-stop (engine stop control) request signals to the PCM.

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• The front/rear climate control unit controls the air mix actuator according to the change in the airflow temperature passing through the heater core or the evaporator during i-stop operation (engine stop control) as follows and corrects the airflow temperature.

― If airflow temperature passing through heater core decreases, air mix actuator is opened in HOT direction

― If airflow temperature passing through evaporator increases, air mix actuator is opened in COLD direction

Caution

• Occupants may hear the sound of the air mix actuator operating because there is no engine sound during the i-stop operation (engine stop control). The airflow temperature control is performed even during i-stop operation (engine stop control), therefore, it does not indicate a system malfunction even if the operation sound of the air mix actuator is heard.

Structure/Construction

Block diagram

Front

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Rear

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System wiring diagram

Front climate control unit type A

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Front climate control unit type B

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Rear climate control unit

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Structural view

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L.H.D.

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R.H.D.

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Operation

Airflow temperature control

1. Based on the airflow temperature setting and the signals (1) from each sensor which change according to the vehicle conditions, the front/rear climate control units perform airflow temperature determination (2) when the ignition is switched ON (engine off or on).

2. The front/rear climate control units operate (3) the front/rear air mix actuators based on the results of the airflow temperature determination and corrections.

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3. The front/rear climate control units detect the current front/rear air mix actuator opening angle based on the potentiometer voltage (4).

4. The front/rear climate control units compare (5) the target actuator opening angle with the potentiometer voltage.

5. When the potentiometer voltage differs from the target actuator opening angle, the front/rear climate control units drive (6) the front/rear air mix actuator motors.

6. When the potentiometer voltage is equal to (7) the target actuator opening angle, the front/rear climate control units stop (8) the front/rear air mix actuator motors.

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Airflow volume control

1. When the ignition is switched ON (engine off or on), the front body control module (FBCM) turns the front/rear blower relays on (1).

2. When the front/rear climate control units receive the blower relay ON signal (2), based on the operation of the airflow volume control dial and the temperature control dial, the airflow mode condition, and the signals from each sensor (3), it performs airflow volume determination (4).

3. The front/rear climate control units send a blower speed signal (5) to the front blower motor/power MOS FET based on the results of the airflow volume determination and corrections.

4. The front blower motor/power MOS FET operate (6) the blower motors based on the blower speed signal.

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Airflow mode control

1. Based on the airflow mode setting and the signals (1) from each sensor which change according to the vehicle conditions, the front/rear climate control units perform airflow mode determination (2) when the ignition is switched ON (engine off or on).

2. The front/rear climate control units operate (3) the front/rear mode actuators based on the results of the airflow mode determination and corrections.

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3. The front/rear climate control units detect the current mode actuator opening angle based on the potentiometer voltage (4).

4. The front/rear climate control units compare (5) the target actuator voltage with the potentiometer voltage.

5. When the potentiometer voltage differs from the target actuator voltage, the front/rear climate control units drive (6) the front/rear mode actuator motors.

6. When the potentiometer voltage is equal to (7) the target actuator voltage, the front/rear climate control units stop (8) the front/rear mode actuator motors.

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Air intake control

1. Based on the air intake mode setting and the signals (1) from each sensor which change according to the vehicle conditions, the front climate control unit performs air intake mode determination (2) when the ignition is switched ON (engine off or on).

2. The front climate control unit operates (3) the air intake actuator based on the results of the air intake mode determination and corrections.

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3. The front climate control unit detects the current air intake actuator opening angle based on the potentiometer voltage (4).

4. The front climate control unit compares (5) the target actuator voltage with the potentiometer voltage.

5. When the potentiometer voltage differs from the target actuator voltage, the front climate control unit drives (6) the air intake actuator motor.

6. When the potentiometer voltage is equal to (7) the target actuator voltage, the front climate control unit stops (8) the air intake actuator motor.

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A/C compressor control

1. Based on the operation of each switch/dial and signals (1) from each sensor which change according to the vehicle conditions, the front climate control unit performs A/C compressor mode determination (2) when the ignition is switched ON (engine off or on).

2. The front climate control unit sends (3) the A/C signal to the PCM based on the results of the A/C compressor mode determination and corrections.

3. The PCM turns the A/C relay on (4) based on the A/C signal and the signals from each sensor which change according to the vehicle conditions.

4. When the A/C relay turns on, the magnetic clutch turns on (5).

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Air conditioner i-stop control (With i-stop)

i-stop (engine stop control) request control (i-stop inhibit/i-stop permit)

• The front climate control unit sends an i-stop inhibit or permit request signal to the PCM according to the operation conditions of the air conditioner system.

• If any of the following i-stop inhibit conditions is met, the front climate control unit sends an i-stop inhibit request signal to the PCM.

i-stop inhibit conditions

1	Ambient temperature is -10 °C {14 °F} or less, or 50 °C {122 °F} or more
2	Blower motor is operating	Defroster is being operated manually
3		Airflow volume setting of airflow volume control dial is at 7th
4		Set temperature is at MAX HOT
5		A/C switch is ON	Set temperature is at MAX COLD
6		Large difference between set temperature and cabin temperature and difference between target airflow temperature and current airflow temperature

• When all of the i-stop inhibit conditions are met, the front climate control unit sends an i-stop permit request signal to the PCM.

Air conditioner system control during i-stop (engine-stop control)

• When the front climate control unit determines that the engine is stopped based on the i-stop condition signal sent from the PCM, it starts the air conditioner system control for the engine-stop condition.

Note

• If the engine is stopped by the i-stop control with the A/C switch turned on, the indicator on the A/C switch is kept turned on.

• Based on the following signals, the front climate control unit calculates the heater core temperature for the engine-stop condition by i-stop control.

― Engine coolant temperature signal at moment engine is stopped which is sent from PCM via CAN communication

― Evaporator temperature

― Blower motor status

― Air mix actuator status

Recovery to normal air conditioner system control

• If any of the following i-stop inhibit conditions is met during air conditioner system control when the engine is stopped, the front climate control unit sends an engine re-start request signal to the PCM.

• After sending an engine restart request signal, the front climate control unit returns to normal air conditioner system control when the engine is restarted.