Climate Control System Description - Overview

Climate Control

The climate control system transmits appropriate signals to each motor based on the information (sunlight, humidity, in-car temperature, outside air temperature) received from each sensor. See below for details.

	Air Mix Control Motor: The system controls the temperature of air coming into the cabin by the air mix control motor adjusting the air mix damper position in order to change the mixing ratio of warm and cold air.
	Mode Control Motor: The system directs the airflow to the specified area by the mode control motor switching the mode control damper position to the "VENT", "HEAT/VENT", "HEAT", "HEAT/DEF", or "DEF".
	Recirculation Control Motor: The recirculation control motor switches the recirculation control damper position to the “FRESH” or “RECIRCULATION”.
	BLOWER MOTOR: The blower motor changes the air volume based on the voltage adjusted by the blower power transistor.

The climate control unit optimizes these controls in order to maintain passenger comfort.

Relationship Between Vent (Air Outlet) Temperature and Actual In-Car Temperature

The climate control unit can automatically control vent temperature (air mix position), blower motor speed, blower intake, and A/C compressor operation to raise or lower the vehicle's interior temperature to match the customer's setting temperature. The actual vent outlet temperature is largely depends upon the difference between the in-car temperature sensor reading and the customer's setting temperature.

Warm-Up Control

If heating is desired, and there is no available heat due to low engine coolant temperature, the climate control unit will slow the fan speed to avoid ventilating unpleasant air. The climate control unit will gradually increase the fan speed as the engine coolant temperature rises.

The conditions that this control becomes effective are as follows:

	Fan speed "AUTO"
	Air outlet position "AUTO", "HEAT", "HEAT/DEF", or "DEF"
	Outside air temperature is less than 68 °F (20 °C)
	Engine coolant temperature sensor is normal.

Low Engine Coolant Temperature Control

When engine coolant temperature is low, the climate control system changes an air outlet position to the DEF. If engine coolant temperature gradually rises, the climate control system changes an air outlet position to the HEAT/DEF. In addition, engine coolant temperature rises, to control the air outlet position by outlet air temperature.

Relationship Between Vehicle Speed and Blower Intake Mode

Because air resistance is different, the air volume is different in the FRESH mode and the RECIRC mode if the fan speed is constant. When a recirculation control damper is "FRESH", fresh air increases as vehicle speed rises. The climate control unit regulates fan speed to make the air volume of the FRESH mode the same as RECIRC mode.

A/C Control

To prevent the evaporator from freezing, the climate control unit switches the A/C compressor ON and OFF based on the evaporator temperature sensor value. While in the automatic operation mode, the climate control unit automatically switches the A/C compressor ON based on the evaporator temperature sensor value, as well as an ambient temperature and humidity.

MAX Control

When the temperature setting is adjusted to “MAX COOL (Lo)” or “MAX HOT (Hi)” and fan speed is set to “AUTO”, the climate control unit overrides automatic control and defaults to the following operation:

	MAX COOL (Lo) “VENT”, blower fan maximum speed, and air mix control door is fully closed on the heater side.
	MAX HOT (Hi) “HEAT”, blower fan maximum speed, and air mix control door is fully open on the heater side. : If the sensor information indicates that the windshield may fog, the air outlet switches to “HEAT/DEF” automatically.