Climate Control System Description - Overview

For locations of each component on vehicle, refer to Component Location Index.

System Diagram

Climate Control

The climate control system transmits appropriate signals to each motor based on the information (sunlight, 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 control 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 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 cold 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.
	Except Type-R: Engine coolant temperature is less than 149 °F (65 °C)
	Type-R: Engine coolant temperature is less than 131 °F (55 °C)

Low Engine Coolant Temperature Control

When engine coolant temperature is low, the climate control system changes an air outlet position to the “DEF”. When the engine coolant temperature increases, the climate control system controls the air outlet position and outlet air temperature automatically.

Relationship Between Vehicle Speed and Blower Intake Mode

Because the air resistance is different between fresh air and recirculated air, the volume of air coming through the vents would be different if the fan speed was constant. When the recirculation control damper is set to “FRESH”, the fresh air flow increases as the vehicle speed increases. The climate control unit regulates the fan speed so that the air volume is the same when “FRESH” or “RECIRCULATION” mode is selected.

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 varies the A/C compressor operation time based on the evaporator temperature sensor value, as well as the outside air temperature.

MAX Control

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

	MAX COOL “RECIRCULATION”, “VENT”, blower fan maximum speed, and A/C system ON.
	MAX HOT “FRESH”, “HEAT”, blower fan maximum speed, and A/C system ON. : If the sensor information indicates that the windshield may fog, the air outlet switches to “HEAT/DEF” automatically.

ECON Control

	A/C compressor load control Reduces load on A/C compressor by slightly raising the target temperature of the evaporator.
	Blower fan speed control Control the blower fan speed low compared to normal operation for an energy-saving operation with low air volume.