The air temperature and the air delivery description and operation are divided into the following:

• HVAC Control Components
• Air Speed and Blower Motor
• Air Delivery
• Heating and A/C Operation
• Recirculation Operation
• Automatic Operation
• Refrigerant System

The body control module (BCM) is a CAN device that interfaces between the operator and the HVAC system to maintain and control desired air temperature and air distribution settings. The BCM provides a device ON-Signal for the HVAC controls. The BCM provides blower, air delivery mode and air temperature control.

The HVAC control contains all switches which are required to control the functions of HVAC and serve as interface between the operator and the BCM. The selected values are passed to the BCM via serial data.

Doors in the HVAC case assembly are used to control air flow. The BCM operates the doors through the use of actuators, with one actuator being used for each door. The system has the following air control doors and associated actuators: mode, left and right temperature, and recirculation.

Each actuator used in the system is a LIN device controlled by the BCM. The BCM supplies a 12 V reference voltage to the actuators, and ground is provided by the wiring harness. When the BCM sends a request message to the actuator, the actuator then operates internal stepper motors to move the door to the required position.

The selected blower motor speed is passed from the controls to the BCM via serial data.

The motor uses a fused B+, ground, control, and speed output signal circuits to operate. The blower motor speed is controlled by increasing or decreasing the voltage drop on the ground side of the blower motor speed control circuit. The BCM provides a low side pulse width modulation (PWM) signal to the blower motor to request a specific motor speed. The blower motor internal circuitry translates the PWM signal and drives the motor accordingly.

The blower motor has a signal wire used to output a speed signal. The speed signal is sent to the BCM, to monitor blower operation.

Afterblow is a feature that dries the evaporator core by operating the blower motor after the engine is turned OFF under certain conditions. This reduces the amount of moisture that can create undesirable odors. For additional information on afterblow, the default setting, and changing the setting, refer to Afterblow Configuration.

Physical air temperature sensors are not used with the system.

The temperature in the air distribution ducts is calculated by the BCM based on information received from the sensors in the system. The BCM uses the calculated temperatures in determining actuator position.

The evaporator air temperature is calculated based on information from the low side B387A Air Conditioning Refrigerant Pressure and Temperature Sensor 1.

The windshield outside moisture, ambient light, and humidity sensor is used by the wiper system to determine exterior moisture, and by the HVAC system for inside windshield temperature and humidity.

The sensors are part of a LIN windshield sensor array, and the sensor values are transmitted to the BCM via serial data.

This sensor assembly provides information to the HVAC system about:

• Relative humidity level at windshield (passenger compartment side)
• Temperature of the windshield (passenger compartment side)
• Temperature of the humidity sensor element

The relative humidity sensor measures the relative humidity of the passenger compartment side of the windshield. It also detects the temperature of the windshield surface on the passenger compartment side. Both values are used as control inputs for the BCM application to calculate the fog risk on windshield compartment side and ability to reduce fuel consumption by decreasing A/C compressor power to a minimum without causing any fog. The sensor will also enable partial recirculation mode in order to improve heat-up performance of the passenger compartment under cold ambient temperature conditions without the risk of mist build-up on the windshield. The humidity sensor element temperature sensor supplies the temperature of the humidity sensor element. It is only needed if the thermal contact between the humidity sensing element and the inside windshield surface is not sufficient.

The sunload and ambient light sensor includes the solar sensor and passenger compartment temperature sensor.

The sensors are part of a LIN device, and the sensor values are transmitted to the BCM via serial data.

Bright or high intensity light can cause the vehicles interior temperature to increase. The HVAC system uses the sensor values and compensates for the increased temperature to maintain the system settings.

The BCM controls the distribution of air by the use of recirculation and mode door actuators. The modes that may be selected are:

• Defrost: windshield outlet
• Panel: dashboard outlets
• Floor: front footwell outlets
• Defog: defrost + floor
• Bi-level: panel + floor
• Tri-level: panel + defrost + floor
• Hi-level: panel + defrost

The desired air distribution mode can be selected with the air distribution switches at the HVAC control. The HVAC control delivers the values to the BCM via serial data. The BCM sends a request to the mode door actuator to move the door to the required position. Depending on the position of the door, air is distributed through various ducts leading to the outlets in the dash. When defrost airflow is active, the BCM will move the recirculation actuator to outside air, to aid in reducing window fogging. When defrost is selected the blower motor will be activated, regardless of the coolant temperature. A/C is available in all modes.

Refer to the owners manual for operation of the HVAC controls and mode selection.

The recirculation switch is integrated into the HVAC control. The selected recirculation setting is sent to the BCM via serial data. The BCM controls the air intake using the recirculation actuator. In recirculation mode the recirculation door is positioned to block outside air from entering and circulate the air within the vehicle. In outside air mode the recirculation door is positioned to route outside air into the vehicle.

Recirculation is only available if the defrost mode is not active. When the defrost mode is active, the recirculation actuator positions the recirculation door so that outside air is circulated to the windshield to reduce fogging.

In automatic mode the values of the sensors are used as inputs for the BCM to calculate the fog risk on the passenger compartment side of the windshield. The A/C compressor and the defrost mode may be activated to prevent or remove fog on the passenger compartment side of the windshield.

In automatic mode, a partial recirculation mode may be commanded to accelerate cabin heating or cooling and reduce energy usage. The recirculation indicator remains illuminated at all times, regardless of the actual operating mode determined by the system.

The purpose of the heating and A/C system is to provide heated and cooled air to the interior of the vehicle. The A/C system will also remove humidity from the interior and reduce windshield fogging. Regardless of the temperature setting, the following may affect the rate that the HVAC system can achieve the desired temperature:

• Recirculation setting
• Difference between inside and desired temperature
• Blower motor speed setting
• Mode setting
• Dashboard outlet open/closed position

The A/C indicator does not indicate the compressor is currently active. The A/C indicator shows that A/C has been requested and the system will activate the compressor as needed.

In automatic operation, the BCM maintains the comfort level inside of the vehicle by controlling the blower motor, the air temperature actuators, mode actuator and recirculation actuator.

The automatic mode indicator shows that the system is in full automatic operation. If an individual setting is changed (excluding temperature), the automatic indicator will turn off, and that function will enter manual control. All other functions will remain under automatic control unless manually changed.

To put the HVAC system in automatic mode, the following is required:

1. The auto switch must be activated.
2. The air temperature switch must not be in either the full hot or full cold position.

Once the desired temperature is reached, the blower motor, mode, recirculation and temperature actuators automatically adjust to maintain the temperature selected. The BCM performs the following functions to maintain the desired air temperature:

• Monitors the following:
• Ambient (outside) air temperature sensor
• Passenger compartment temperature sensor
• Front duct air temperatures
• Auxiliary duct air temperature sensor
• Windshield temperature and inside moisture sensor
• Evaporator temperature sensor
• Ambient light/sunload sensor
• Regulate the blower motor speed
• Regulate the rear blower motor speed
• Position the air temperature actuators
• Position the mode door actuators
• Position the recirculation actuator

When the temperature setting is set to full hot, the blower speed will increase gradually as condenser heat becomes available. When normal condenser operating temperature is reached the blower stays on high speed and the air temperature actuators stays in the full heat position.

When the temperature setting is set to full cold, the blower will immediately operate at high speed and the air temperature actuators move to full cold position. The mode actuator moves to the panel position and the recirculation actuator moves to the recirculation position.

Under cold ambient temperatures, the automatic HVAC system provides heat in the most efficient manner. The operator can select an extreme temperature setting but the system will not warm the vehicle any faster. Under warm ambient temperatures, the automatic HVAC system also provides air conditioning in the most efficient manner. Selecting an extreme cool temperature will not cool the vehicle any faster.

In automatic mode the values of the windshield temperature and inside moisture sensor are used as control inputs for the BCM application to calculate the fog risk on the passenger compartment side of the windshield. Defrost mode may be activated to prevent or remove fog on the passenger compartment side of the windshield. The sensor may also enable partial recirculation mode in order to improve heat-up performance of the passenger compartment under cold ambient temperature conditions without the risk of mist build-up on the windshield.

This vehicle is equipped with the Battery Electric Vehicle Harmonized Enhanced Active Thermal System (bevHEAT) and combines two normally independent systems to form one integrated thermal system. This combination results in improved overall thermal efficiency and range. The refrigerant system is utilized to heat as well as cool the vehicle cabin using a condensing heater and evaporator. This differs from more traditional refrigerant systems that are only used to cool the vehicle cabin.

Additionally the system utilizes a coolant loop with a series of pumps and multi-position valves to remove generated heat from the propulsion components. The thermal energy in the coolant loop interacts with the refrigerant loop through a heat exchanger, and can be utilized to for providing cabin heat.

The system is also activated during charging events in order to keep the high voltage battery at an optimal temperature. Thermal energy removed during charging events can be stored and used to provide cabin heat during the next drive cycle if needed.

For additional information on the refrigerant system, refer to Heating and Air Conditioning System Description and Operation.

For additional information on the propulsion heating and cooling section of the system, refer to Hybrid/EV Cooling System Description and Operation.

The compressor is used to provide refrigerant flow in the refrigerant loop to heat and cool the cabin, help dehumidify the air in a defrost mode, help maintain the battery temperature, and help maintain the temperature of the propulsion system components. The compressor uses a 3-phase alternating current, high voltage electric motor to operate. It has an on-board inverter that takes high voltage direct current from the vehicle's high voltage battery and inverts it to alternating current for the motor.

The compressor contains an integrated control module. The compressor control module operates and monitors the A/C compressor, and communicates with other modules via serial data. The compressor control module reports any malfunctions to the K18A Battery Energy Control Module 1, which sets the appropriate DTC for the malfunction.

The K18A Battery Energy Control Module 1 uses values from the refrigerant pressure sensors, refrigerant temperature sensors, duct temperature sensors, ambient air temperature sensor , passenger compartment temperature sensor, battery temperature sensors, battery coolant temperature sensors, and battery coolant pumps to determine the speed at which the compressor will operate.

Three combination pressure and temperature sensors are used in the refrigerant system.

The B387A Air Conditioning Refrigerant Pressure and Temperature Sensor 1 monitors the pressure and temperature of the refrigerant at the compressor inlet.

The B387B Air Conditioning Refrigerant Pressure and Temperature Sensor 2 monitors the pressure and temperature of the refrigerant at the compressor outlet.

The B387C Air Conditioning Refrigerant Pressure and Temperature Sensor 3 monitors the pressure and temperature of the refrigerant at the expansion valve inlet.

Each sensor contains a 2-wire negative temperature coefficient thermistor and a 3-wire piezoelectric pressure transducer in the sensor assembly. The circuits to operate and monitor the sensors are provide by the K18A Battery Energy Control Module 1.

The temperature sensor operates using a signal and low reference circuits. As the temperature increases, the sensor resistance decreases. The sensor varies the signal voltage between 0.2–4.8 V.

The pressure sensor operates using a 5 V reference, signal and low reference circuits. Changes in the refrigerant pressure cause the sensor signal to the control module to vary. As the pressure increases, the sensor signal increases. The sensor varies the signal voltage between 0.25–4.75 V.

Four additional temperature sensors are used in the refrigerant system.

The B222D Air Conditioning Refrigerant Temperature Sensor 4 monitors the temperature of the refrigerant at the chiller outlet.

The B222E Air Conditioning Refrigerant Temperature Sensor 5 monitors the temperature of the refrigerant at the front evaporator outlet.

The B222F Air Conditioning Refrigerant Temperature Sensor 6 monitors the temperature of the refrigerant at the condensing heater (also called the cabin condenser) outlet.

The B222H Air Conditioning Refrigerant Temperature Sensor 8 monitors the temperature of the refrigerant at the external condenser outlet.

Each sensor is a 2-wire negative temperature coefficient thermistor. The circuits to operate and monitor the sensors are provided by the K18A Battery Energy Control Module 1.

The temperature sensor operates using a signal and low reference circuits. As the temperature increases, the sensor resistance decreases. The sensor varies the signal voltage between 0.2–4.8 V.

Refrigerant flow valves are used to control the flow of refrigerant to the condensers. The valves are LIN devices utilizing a stepper motor to control the position of the valve, with a sensor to provide position feedback. The K16A Battery Energy Control Module 1 sends a LIN serial data message to request the valves to move to the calculated position to achieve the desired refrigerant flow.

The Q110 Air Conditioning Condenser Refrigerant Flow Valve– External controls the flow of refrigerant going to the external condenser (also called the front-end condenser). This is the larger condenser, and it is used to reject heat from the system to the atmosphere.

The Q111 Air Conditioning Condenser Refrigerant Flow Valve– Heater controls the flow of refrigerant going to the condensing heater (also called the cabin condenser). This is the smaller condenser, used to maintain cabin comfort.

A fused B+ circuit supplies voltage to the valve, and ground is provided by the wiring harness. The K16A Battery Energy Control Module 1 sends a LIN serial data message to request the valve to move to the calculated position to achieve the desired setting.

The electronic expansion valves used in the refrigerant system are stepper motors controlled via serial data. The stepper motor moves a needle to open or close an orifice that allows refrigerant to pass. Valve position is determined by the number of times the stepper motor has been pulsed.

The Q112 Air Conditioning Cooler Electronic Expansion Valve is used for the drive motor battery coolant cooler (chiller).

The Q113 Air Conditioning Evaporator Electronic Expansion Valve is used for the passenger cabin evaporator.

A fused B+ circuit supplies voltage to the valve, and ground is provided by the wiring harness. The K16A Battery Energy Control Module 1 sends a LIN serial data message to request the valve to move to the calculated position to achieve the desired setting.