Dual Automatic Temperature Control
DUAL AUTOMATIC TEMPERATURE CONTROL
The dual automatic temperature control (DATC) module analyzes input from the following major sources:
- temperature, function and blower selection (made by the vehicle occupants)
- in-vehicle temperature
- in-vehicle humidity (Navigator only)
- ambient temperature
- sunload
- vehicle speed
- engine coolant temperature
Using these inputs, the DATC module determines the correct conditions for the following outputs:
- A/C compressor operation
- blower speed
- LH side temperature blend door position
- RH side temperature blend door position
- panel airflow door position
- airflow door positions
- coolant control valve
Control System Inputs - DATC
DATC Module (Climate Control Assembly)
The DATC module:
- is located in the instrument panel.
- has a vacuum fluorescent display for displaying set temperature, function and diagnostic trouble codes (DTCs).
- utilizes an on-board diagnostic (OBD) feature to supply the technician with diagnostic trouble codes (DTCs). These DTCs direct the technician to the inoperative component.
Steering Wheel Audio/Climate Control Switch
The steering wheel audio/climate control switch:
- is located on the right side of the steering wheel.
- allows the driver to adjust the passenger compartment temperature setting and manually override the blower motor speed setting.
Ambient Air Temperature Sensor
The ambient air temperature sensor:
- is located in front of the condenser core.
- provides a resistance value to a reference voltage from the DATC module that is proportional to the outside ambient temperature. The resulting voltage is then returned to the DATC module where it is interpreted as a temperature reading.
In-Vehicle Temperature/Humidity Sensor - Navigator
The in-vehicle temperature/humidity sensor operates in the following manner:
- A thermistor in the in-vehicle temperature/humidity sensor measures air temperature inside the passenger compartment.
- A humidity transducer in the in-vehicle temperature/humidity sensor measures in-vehicle humidity.
- A hose and elbow is connected between the plenum chamber and the in-car temperature/humidity sensor.
- Airflow through the plenum chamber creates a venturi-type suction through the hose which draws passenger compartment air through the in-vehicle temperature/humidity sensor and across the thermistor and humidity transducer.
In-Vehicle Temperature/Sensor - Expedition
The in-vehicle temperature sensor operates in the following manner:
- A thermistor in the in-vehicle temperature sensor measures air temperature inside the passenger compartment.
- A hose and elbow is connected between the plenum chamber and the in-vehicle temperature sensor.
- Airflow through the plenum chamber creates a venturi-type suction through the hose which draws passenger compartment air through the in-vehicle temperature sensor and across the thermistor.
Dual-Zone Solar Amplifier (Sunload Sensor) - Navigator
The solar amplifier is a dual-zone type that supplies separate information to the DATC module indicating LH side and RH side sunload.
Single-Zone Solar Amplifier (Sunload Sensor) - Expedition
The solar amplifier supplies information to the DATC module indicating sunload.
Control System Outputs - DATC
Automatic Temperature Control (ATC) Solenoid and Manifold
The ATC solenoid and manifold:
- is located on the plenum chamber in front of the front floor console.
- is controlled by the DATC module.
- uses solenoid-type valves to distribute manifold vacuum to the vacuum control motors based on the settings of the DATC module.
Blower Motor Speed Control
The motor blower speed control:
- is located on the heater core and evaporator core housing near the blower motor.
- converts low power signals from the DATC module to a high current, variable ground feed for the blower motor.
- varies the blower motor speed and is controlled by the DATC module software.
- has a delay function to provide a gradual increase or decrease in blower motor speed under all conditions.
- controls the integral high blower speed relay which is engaged when maximum fan speed is selected.
Temperature Blend Door Actuators
The DATC system utilizes two temperature blend door actuators to control two separate temperature blend doors that independently vary the LH and RH side temperature settings, as desired. The temperature blend door actuators:
- are located on the plenum chamber.
- move the temperature blend doors on command from the DATC module.
- contain a reversible electric motor and a potentiometer. The potentiometer wiper is connected to the actuator output shaft and moves with the output shaft to indicate the position of the temperature blend door.
- receive a reference voltage to one end of the potentiometer. The voltage available at the wiper indicates the position of the potentiometer. The expressed value of the actuator wiper voltage is sent to the DATC module and is matched with an expected wiper voltage value. The DATC module then drives the actuator motor in whichever direction is necessary to make the actuator wiper voltage match the expected DATC module wiper voltage value.
Vacuum Control Motors
The three vacuum control motors have the following characteristics:
- They are actuated by the ATC solenoid and manifold based on input from the DATC module.
- They position the mode doors to direct system airflow to the vehicle interior as determined by the DATC module settings.
- The air inlet door vacuum control motor is a single-diaphragm actuator with a single vacuum source.
- The airflow mode door vacuum control motors are double-diaphragm actuators with two separate vacuum sources to allow the actuator to fully retract or partially retract.
- When vacuum is applied to both vacuum sources, the actuator will fully retract.
- When vacuum is applied only to the partial stage vacuum source, the actuator will partially retract.
Coolant Control Valve
The coolant control valve is actuated by the coolant control valve vacuum circuit. When the coolant control valve is closed (at full vacuum), coolant flow through the heater core is shut off and A/C cooling efficiency is increased.