System Operation
Climate Control - DATC
System Operation
System Diagram
DATC (Dual Automatic Temperature Control)
Network Message Chart
DATC (Dual Automatic Temperature Control) without Sony(R) Sound
Module Network Input Messages - PCM (Powertrain Control Module)
Module Network Input Messages - HVAC (Heating, Ventilation, and Air Conditioning) Module
DATC (Dual Automatic Temperature Control) with Sony(R) Sound
Module Network Input Messages - APIM (Accessory Protocol Interface Module)
Module Network Input Messages - PCM (Powertrain Control Module)
Module Network Input Messages - HVAC (Heating, Ventilation, and Air Conditioning) Module
The Refrigerant Cycle
During stabilized conditions (A/C (Air Conditioning) system shutdown), the refrigerant pressures are equal throughout the system. When the A/C (Air Conditioning) compressor is in operation, it uses a piston pump to compress the cool vapor, causing it to become high-temperature/high-pressure vapor. The high-temperature/high-pressure vapor is then released into the top of the A/C (Air Conditioning) condenser core.
The A/C (Air Conditioning) condenser, being close to ambient temperature, causes the refrigerant vapor to condense into a liquid when heat is removed from the refrigerant by ambient air passing over the fins and tubing. The now liquid refrigerant, still at high pressure, exits from the bottom of the A/C (Air Conditioning) condenser and enters the inlet side of the A/C (Air Conditioning) receiver/drier (integral to the condenser). The receiver/drier is designed to remove moisture and contaminants from the refrigerant system.
The outlet of the receiver/drier is connected to the TXV (Thermostatic Expansion Valve). The TXV (Thermostatic Expansion Valve) provides the orifice, which is the restriction in the refrigerant system which separates the high and low pressure sides of the A/C (Air Conditioning) system. As the liquid refrigerant passes across this restriction, its pressure and boiling point are reduced.
The liquid refrigerant is now at its lowest pressure and temperature. As it passes through the A/C (Air Conditioning) evaporator, it absorbs heat from the airflow passing over the plate/fin sections of the A/C (Air Conditioning) evaporator. This addition of heat causes the refrigerant to boil (convert to gas). The now cooler air can no longer support the same humidity level of the warmer air and this excess moisture condenses on the exterior of the evaporator coils and fins and drains outside the vehicle.
The refrigerant cycle is now repeated with the A/C (Air Conditioning) compressor again increasing the pressure and temperature of the refrigerant.
A thermistor which monitors the temperature of the air that has passed through the evaporator core controls A/C (Air Conditioning) clutch cycling. If the temperature of the evaporator core discharge air is low enough to cause the condensed water vapor to freeze, the A/C (Air Conditioning) clutch is disengaged by the PCM (Powertrain Control Module).
The high-side line pressure is also monitored so that A/C (Air Conditioning) compressor operation is interrupted if the system pressure becomes too high or is determined to be too low (low charge condition).
The A/C (Air Conditioning) compressor relief valve opens and vents refrigerant to relieve unusually high system pressure.
Control System Logic
Climate Control System Network Communication
The controls for the climate control system are in one or more locations depending on vehicle option content:
- DATC (Dual Automatic Temperature Control) module
- FCIM (Front Controls Interface Module) if equipped with Sony(R) sound
- FDIM (Front Display Interface Module) (part of APIM (Accessory Protocol Interface Module)), if equipped with Sony(R) sound
Without Sony(R) Sound
The customer inputs are directly inputted in to the DATC (Dual Automatic Temperature Control) module.
When A/C (Air Conditioning) is selected, the HVAC (Heating, Ventilation, and Air Conditioning) module sends the request to the BCM (Body Control Module) over the MS-CAN (Medium Speed Controller Area Network). The BCM (Body Control Module) then sends the request to the PCM (Powertrain Control Module) over the HS-CAN (High Speed Controller Area Network).
On vehicles with Sony(R) Sound the touch screen and voice commands can be used for climate control inputs.
Controls and Compressor Cycling
Climate Control Commands/ A/C (Air Conditioning) Request
Climate control commands are inputted through the HVAC (Heating, Ventilation, and Air Conditioning) module and on vehicles equipped with Sony(R) Sound inputs can also be commanded through voice commands or the touch screen.
When the A/C (Air Conditioning) is requested, the HVAC (Heating, Ventilation, and Air Conditioning) module sends the message over the MS-CAN (Medium Speed Controller Area Network) to the BCM (Body Control Module). The BCM (Body Control Module) then forwards the message to the PCM (Powertrain Control Module) module over the HS-CAN (High Speed Controller Area Network).
Compressor Clutch
When A/C (Air Conditioning) is requested and A/C (Air Conditioning) line pressures allows, a ground is provided to the A/C (Air Conditioning) clutch relay coil from the PCM (Powertrain Control Module), energizing the A/C (Air Conditioning) clutch relay. When the PCM (Powertrain Control Module) energizes the relay, voltage is supplied to the A/C (Air Conditioning) compressor clutch field coil from the relay.
A/C (Air Conditioning) Compressor Cycling
The evaporator discharge air temperature sensor is an input to the BCM (Body Control Module) and is relayed to the PCM (Powertrain Control Module) over the HS-CAN (High Speed Controller Area Network). The evaporator discharge air temperature sensor prevents icing of the evaporator core by measuring the temperature of the airflow immediately after the evaporator core. An accurate evaporator temperature is critical for compressor engagement. The PCM (Powertrain Control Module) uses the temperature measurement to regulate the on and off time of the A/C (Air Conditioning) compressor to maintain the evaporator temperature within an acceptable temperature range.
The PCM (Powertrain Control Module) monitors the discharge pressure measured by the A/C (Air Conditioning) pressure transducer. The PCM (Powertrain Control Module) interrupts A/C (Air Conditioning) compressor operation in the event the A/C (Air Conditioning) pressure transducer indicates high system discharge pressures. It is also used to sense low charge conditions. If the pressure is below a predetermined value for a given ambient temperature, the PCM (Powertrain Control Module) does not allow the A/C (Air Conditioning) clutch to engage.
Sensor Inputs
The HVAC (Heating, Ventilation, and Air Conditioning) module adjusts the air inlet door depending on the humidity measured by the in-vehicle temperature and humidity sensor. If the vehicle cabin becomes too humid and recirculated air is not selected, the HVAC (Heating, Ventilation, and Air Conditioning) module adjusts the air inlet door to allow more recirculated air. When the humidity level drops, it adjusts back to fresh air. The HVAC (Heating, Ventilation, and Air Conditioning) module also adjusts the system based on in-vehicle temperature.
The autolamp/sunload sensor supplies information to the HVAC (Heating, Ventilation, and Air Conditioning) module indicating the intensity of the sun on the vehicle and the HVAC (Heating, Ventilation, and Air Conditioning) module adjusts the system based on the intensity.
Air Handling
The defrost mode door, panel/floor mode door, temperature blend door and air inlet mode door actuators each use a potentiometer to sense the door position to the HVAC (Heating, Ventilation, and Air Conditioning) module.
When an airflow mode, desired driver or passenger temperature or fresh air or recirculation mode is selected the HVAC (Heating, Ventilation, and Air Conditioning) module drives the actuator motor in the direction necessary to make the actuator position agree with the expected HVAC (Heating, Ventilation, and Air Conditioning) module position to be obtained.
The HVAC (Heating, Ventilation, and Air Conditioning) module sends a PWM (Pulse Width Modulated) signal to the blower motor speed control to control the blower speed. The blower speed control provides variable ground feed for the blower motor. A delay function provides a gradual increase or decrease in blower motor speed under all conditions.
AUTO
When AUTO is selected:
- the HVAC (Heating, Ventilation, and Air Conditioning) system operates in a manner to achieve and maintain the temperature set by the operator.
- the air inlet door is automatically controlled by the HVAC (Heating, Ventilation, and Air Conditioning) module based on the temperature setting.
- the mode door is automatically controlled by the HVAC (Heating, Ventilation, and Air Conditioning) module based on the temperature setting.
- the temperature blend doors are automatically controlled by the HVAC (Heating, Ventilation, and Air Conditioning) module, based on the temperature setting.
- the A/C compressor is automatically controlled by the HVAC (Heating, Ventilation, and Air Conditioning) module, based on the temperature setting. The A/C (Air Conditioning) compressor does not operate if the outside temperature is below approximately 6°C (42.8°F).
- the blower motor speed is automatically controlled by the HVAC (Heating, Ventilation, and Air Conditioning) module based on the temperature setting, but can be manually overridden.
OFF
When OFF is selected:
- the air inlet door closes, preventing outside air and allowing only recirculated air.
- the blower motor is off.
MAX AC
When MAX A/C is selected:
- the air inlet door closes, preventing outside air and admits only recirculated air.
- the recirculated air indicator is illuminated (recirculated air forced on).
- the mode doors direct airflow to the instrument panel registers.
- the temperature blend doors move to the full cool position. Air temperature can be manually overridden.
- the A/C button is illuminated.
- the A/C (Air Conditioning) compressor operates if the outside temperature is above approximately 6°C (42.8°F).
- the blower motor is commanded to the highest speed. The blower motor speed is adjustable.
PANEL
When PANEL mode is selected:
- the recirculated air request button is enabled. If the recirculated air request button is selected (indicator on), the air inlet door closes, preventing outside air from entering the passenger compartment. If the recirculated air request button is not selected (indicator off), the air inlet door opens, allowing only outside air into the passenger compartment.
- the mode doors direct airflow to the instrument panel registers.
- blended air temperature is available. Only when A/C (Air Conditioning) compressor operation has been selected by pressing the A/C button (indicator on) can the airflow temperature be cooled below the outside air temperature.
- the blower motor is on and the speed is adjustable.
PANEL-FLOOR
When PANEL/FLOOR mode is selected:
- the recirculated air request button is enabled. If the recirculated air request button is selected (indicator on), the air inlet door closes, preventing outside air from entering the passenger compartment. If the recirculated air request button is not selected (indicator off), the air inlet door opens, allowing only outside air into the passenger compartment.
- the mode doors direct airflow to the floor duct and the instrument panel registers. A small amount of airflow from the side window demisters and defrost duct is present.
- blended air temperature is available. Only when A/C (Air Conditioning) compressor operation has been selected by pressing the A/C button (indicator on) can the airflow temperature be cooled below the outside air temperature.
- the blower motor is on and the speed is adjustable.
FLOOR
When FLOOR mode is selected:
- the recirculated air request button is enabled. If the recirculated air request button is selected (indicator on), the air inlet door closes, preventing outside air from entering the passenger compartment. If the recirculated air request button is not selected (indicator off), the air inlet door opens, allowing only outside air into the passenger compartment.
- the mode doors direct airflow to the floor duct. A small amount of airflow from the defroster duct and side window demisters is present.
- blended air temperature is available. Only when A/C (Air Conditioning) compressor operation has been selected by pressing the A/C button (indicator on) can the airflow temperature be cooled below the outside air temperature.
- the blower motor is on and the speed is adjustable.
FLOOR-DEFROST
When FLOOR/DEFROST mode is selected:
- the recirculated air request button is enabled. If the recirculated air request button is selected (indicator on), the air inlet door closes, preventing outside air from entering the passenger compartment. If the recirculated air request button is not selected (indicator off), the air inlet door opens, allowing only outside air into the passenger compartment.
- the mode doors direct airflow to the floor duct, the defroster duct and the side window demisters.
- blended air temperature is available. Only when A/C (Air Conditioning) compressor operation has been selected by pressing the A/C button (indicator on) can the airflow temperature be cooled below the outside air temperature.
- the blower motor is on and the speed is adjustable.
DEFROST
When DEFROST mode is selected:
- the recirculated air request button is disabled. The air inlet door opens, allowing only outside air into the passenger compartment.
- the mode doors direct airflow to the defroster duct and side window demisters. A small amount of airflow from the floor duct is present.
- the A/C is turned on in defrost. The Air Conditioning (A/C) compressor operates as long as the outside temperature is above approximately 6°C (42.8°F).
- blended air temperature is available.
- the blower motor is on and the speed is adjustable.