Ambient and inner temperatures.
DENSO climate control module operates AC as needed to maintain preset temperatures for either side.

 

So. The AC is automatically turned on/off based on how cool the outside temp is?

 

AC are made/tuned to maintain approximately 40 F difference below the ambient, in COOL setting, which is lowest AC temp setting. COOL or LOW. Otherwise, it will mix warm and cold air to reach desired salon temp. If it's too cold outside, for AC to, actually, operate properly, it should not engage. GM vehicles, for example, have 33F as cut off ambient temp. .
That said, if you have defrost on or windows chosen, it automatically engages AC for humidity control. On some vehicles, you can't even tell, as AC light does not come up. It's safety feature.

Might be easier, if you explained, why the question.

 

AC are made/tuned to maintain approximately 40 F difference below the ambient, in COOL setting, which is lowest AC temp setting. COOL or LOW. Otherwise, it will mix warm and cold air to reach desired salon temp. If it's too cold outside, for AC to, actually, operate properly, it should not engage. GM vehicles, for example, have 33F as cut off ambient temp. .
That said, if you have defrost on or windows chosen, it automatically engages AC for humidity control. On some vehicles, you can't even tell, as AC light does not come up. It's safety feature.

Might be easier, if you explained, why the question.

After reading the manual I get the impression that in ECO mode the computer decides if the AC compressor is used or not. From my reading I assume that if the outside temp is cool enough to reach the desired inside temp the system will not engage the AC compressor and use the outside air and turn off the AC light/button. This is for fuel economy. This can be over ridden by pressing the AC button. Am I correct?

 

ECO mode does strange things to AC, so does Auto.
It is basic safety feature - if ambient is below AC ability to operate properly, it will not run. If it's 50 outside and you want 60 inside, why run AC?

Neural Network Control
In previous automatic air conditioning systems, the A/C ECU determined the required outlet air
temperature and blower air volume in accordance with a calculation formula and based on information
received from the sensors. However, because people’s senses are rather complex, a given temperature is
sensed differently, depending on the environment in which the person is situated. For example, a given
amount of solar radiation can feel comfortably warm in a cold climate, or extremely uncomfortable in a
hot climate. Therefore, as a technique for effecting a higher level of control, a neural network is used in
the automatic air conditioning system. With this technique, data that has been collected under varying
environmental conditions is stored in the A/C ECU. The A/C ECU can then effect control to provide
enhanced air conditioning comfort.
The neural network control consists of neurons in the input layer, intermediate layer, and output layer. The
input layer neurons process the input data of the outside temperature, the amount of sunlight, and the room
temperature based on the outputs of the switches and sensors, and output them to the intermediate layer
neurons. Based on this data, the intermediate layer neurons adjust the strength of the links among the
neurons. The sum of these is then calculated by the output layer neurons in the form of the required outlet
temperature, solar correction, target airflow volume, and outlet mode control volume. The A/C ECU
controls the servo motors and blower motor in accordance with the control volumes that have been
calculated by the neural network control.
Compressor Speed Control
The A/C ECU calculates the target compressor speed based on the target evaporator temperature
(calculated from the room temperature sensor, outside temp. sensor, and solar sensor) and the actual
evaporator temperature detected by the evaporator temperature sensor. Then, the A/C ECU transmits the
target speed to the THS ECU. The THS ECU controls the A/C inverter based on the target speed data
in order to control the compressor to a speed that suits the operating condition of the air conditioning
system.
The A/C ECU calculates the target evaporator temperature, which includes corrections based on the
room temperature sensor, outside temp. sensor, solar sensor, and evaporator temperature sensor.
Accordingly, the A/C ECU controls the compressor speed to an extent that does not inhibit the proper
cooling performance or defogging performance. As a result, comfort and low fuel consumption can be
reali
Eco Mode Control
General
Eco mode control limits the air conditioning system performance during heating and cooling and
increases the amount of engine OFF time, thus improving the fuel economy.
Eco mode control is activated by pressing the momentary type ECO switch on the instrument panel.
“ECO” is displayed on the heater control panel LCD during this control.

Heating Mode
The required engine coolant temperature when starting the engine when the vehicle is stopped differs
from that when the vehicle is running. Therefore, the fuel economy has been improved by increasing the
amount of engine-off time when the vehicle is stopped.
When the ECO switch is turned ON during heating, the A/C ECU stops the PTC heater operation.
Therefore, it takes a longer time to reach the set temperature than while the ECO switch is OFF.
Engine coolant temperatures fluctuate greatly between when the vehicle is running and the vehicle is
stopped. The blower level changes accordingly.
Cooling Mode
When the ECO switch is turned ON during cooling, the A/C ECU limits the power consumption of the
electric inverter compressor in accordance with the room temperature.
The A/C ECU does not limit the power consumption very much (C2 shown in the graph below), and
prioritizes decreasing the room temperature when the room temperature is high (T2 or above). When the
room temperature decreases to T1 or below, the A/C ECU limits the power consumption of the electric
inverter compressor C1 and restrains the cooling performance. This prevents the SOC (state of charge)
of the HV battery from decreasing and increases the amount of engine OFF time, improving the fuel
economy.
NOTE: ECO mode control is performed only when the blower motor is ON. When the ECO switch is
turned ON while the blower motor is OFF, the ECO switch indicator light and the heater control
panel LCD display illuminate, but ECO mode control is not performed.
During cooling under ECO mode control, the room temperature is maintained at 25C (77F)
even if the set temperature is below 25C (77F). Since the power consumption of the electric
inverter compressor is limited under ECO mode control, this does not indicate a malfunction.
To decrease the room temperature to below 25C (77F), the MAX COLD temperature [18C
(64.4F)] must be selected or ECO mode control must be canceled by turning the ECO switch
OFF.

 

That is interesting, thank you. I just thought it was an on/off switch.

 

Naahh. On/off is as much useful, as the gas pedal in those cars. "neural network" knows better.

 

I wish the "neural network" would notice that I am constantly changing my AC controls down to 66 on a cold morning and up to 72 on a hot afternoon and adjust the output temp so I don't have to do that. When I set it to 70, that's where I want it.

 

Oh, no, you are just confused. Neural network knows better, what is good for you.