Control Components
Control Components
Electronic Manual Temperature Control (EMTC)
The Electronic Manual Temperature Control (EMTC) components are used to select the following:
- Air inlet source (outside or recirculated)
- Blower motor speed
- Discharge air temperature (temperature blend)
- Discharge air location (defrost, panel, floor)
- A/C compressor operation
Control System Input
HVAC Module
The EMTC (Electronic Manual Temperature Control) system uses a remote HVAC module that is separate from the control interface. The Front Controls Interface Module (FCIM) provides the interface for the vehicle occupants to control the climate control system. When selections are made, the FCIM (Front Controls Interface Module) communicates the selections to the HVAC module through the vehicle module communication network. The remote HVAC module controls the climate control system based on the FCIM (Front Controls Interface Module) selections. The remote HVAC module is located under the driver side of the instrument panel.
Control System Outputs
The EMTC (Electronic Manual Temperature Control) system has 4 control system outputs.
Blower Motor Speed
The blower motor speed control controls the blower motor speed by converting low power signals from the HVAC module to a high current, variable ground feed for the blower motor. A delay function provides a gradual increase or decrease in blower motor speed under all conditions.
The blower motor speed control is located on the heater core and evaporator core housing behind the glove compartment.
Temperature Blend Door Position
The temperature blend door actuator moves the temperature blend door on command from the HVAC module.
The temperature blend door actuator contains a reversible electric motor and a potentiometer. The potentiometer circuit consists of a 5-volt reference signal connected to one end of a variable resistor, and a signal ground connected to the other. A signal circuit is connected to a contact wiper, which is driven along the variable resistor by the actuator shaft. The signal to the HVAC module from the contact wiper indicates the position of the temperature blend door. The HVAC module drives the actuator motor in whichever direction is necessary to make the actuator contact wiper voltage agree with the expected HVAC module contact wiper voltage value.
Airflow Mode Door Position
The airflow mode door actuator uses a cam and lever assembly to position the airflow mode doors on command from the HVAC module. The mode door actuator contains a reversible electric motor and potentiometer. The potentiometer allows the HVAC module to monitor the position of the airflow mode doors. The potentiometer circuit consists of a 5-volt reference signal connected to one end of a variable resistor, and a signal ground connected to the other. A signal circuit is connected to a contact wiper, which is driven along the variable resistor by the actuator shaft. The signal to the HVAC module from the contact wiper indicates the position of the airflow mode doors.
Air Inlet Mode Door Position
The air inlet mode door actuator moves the air inlet door between the fresh and RECIRC positions on command from the HVAC module. The air inlet mode door actuator is driven to, and automatically stops at, the full RECIRC or full fresh air inlet position and does not require a potentiometer circuit to monitor its position.
Dual-Zone Electronic Automatic Temperature Control (EATC)
The dual-zone Electronic Automatic Temperature Control (EATC) module analyzes input from the following sources:
- Temperature, airflow mode, blower, A/C and RECIRC selection (made by the vehicle occupants)
- In-vehicle temperature sensor
- Ambient temperature sensor
- Solar radiation sensor (sunload sensor)
- Evaporator temperature sensor
- Vehicle speed
- Engine coolant temperature
Using these inputs, the dual-zone HVAC module determines the correct conditions for the following outputs:
- A/C compressor operation
- Blower speed
- Temperature blend door position
- Airflow mode door position
- Air inlet door position
Control System Inputs
The dual-zone EATC (Electronic Automatic Temperature Control) system has 4 control system inputs.
HVAC Module
The EATC (Electronic Automatic Temperature Control) system uses a remote HVAC module that is separate from the control interface. The Front Controls Interface Module (FCIM) provides the interface for the vehicle occupants to control the climate control system. When selections are made, the FCIM (Front Controls Interface Module) communicates the selections to the HVAC module through the Medium Speed Controller Area Network (MS-CAN), and the HVAC module adjusts the climate control system components to achieve the desired state. When the climate control system is operating in AUTO mode via command from the FCIM (Front Controls Interface Module), the required climate control system settings are determined by the HVAC module. The HVAC module then adjusts the climate control system components to the desired state. The remote HVAC module is located under the driver side of the instrument panel.
In-Vehicle Temperature Sensor
The in-vehicle temperature sensor contains a thermistor which measures the in-vehicle air temperature and sends that reading to the HVAC module. An aspirator hose is connected between the heater core and evaporator core housing and the in-vehicle temperature sensor. The aspirator hose uses airflow through the heater core and evaporator core housing to create a venturi-type suction to draw in-vehicle air through the in-vehicle temperature sensor (across the thermistor).
Solar Radiation Sensor (Sunload Sensor)
The solar radiation sensor supplies information to the HVAC module indicating sunload.
Ambient Temperature Sensor
The ambient temperature sensor signal is received by the PCM and indicates the outside air temperature. The ambient temperature sensor is located in front of the radiator on the radiator support bolster.
Control System Outputs
The dual-zone EATC (Electronic Automatic Temperature Control) system has 4 control system outputs.
Blower Motor Speed Control
The blower motor speed control controls the blower motor speed by converting low power signals from the HVAC module to a high current, variable ground feed for the blower motor. A delay function provides a gradual increase or decrease in blower motor speed under all conditions.
Temperature Blend Door Actuators
The dual-zone EATC (Electronic Automatic Temperature Control) system uses 2 temperature blend door actuators to control 2 separate temperature blend doors. The temperature blend doors independently vary the LH and RH side temperature settings, as desired. The temperature blend door actuators each contain a reversible electric motor and a potentiometer. The potentiometer circuit consists of a 5-volt reference signal connected to one end of a variable resistor, and a signal ground connected to the other. A signal circuit is connected to a contact wiper, which is driven along the variable resistor by the actuator shaft. The signal to the HVAC module from the contact wiper indicates the position of the temperature blend door. The HVAC module drives the actuator motor in whichever direction is necessary to make the actuator contact wiper voltage agree with the expected HVAC module contact wiper voltage value.
Airflow Mode Door Actuator
The airflow mode door actuator uses a cam and lever assembly to position the airflow mode doors on command from the HVAC module. The airflow mode door actuator contains a reversible electric motor and potentiometer. The potentiometer allows the HVAC module to monitor the position of the airflow mode doors. The potentiometer circuit consists of a 5-volt reference signal connected to one end of a variable resistor, and a signal ground connected to the other. A signal circuit is connected to a contact wiper, which is driven along the variable resistor by the actuator shaft. The signal to the HVAC module from the contact wiper indicates the position of the airflow mode doors.
Air Inlet Mode Door Actuator
The air inlet mode door actuator moves the air inlet door between the fresh and RECIRC positions on command from the HVAC module. The air inlet mode door actuator is driven to, and automatically stops at, the full RECIRC or full fresh air inlet position and does not require a potentiometer circuit to monitor its position.