Climate Control System
Climate Control System
WARNING: Take the following precautions when repairing an air conditioning system containing R-134a:
- Always wear safety goggles.
- Avoid contact with liquid refrigerant R-134a. R-134a vaporizes at approximately -25°C (-13°F) under atmospheric pressure and will freeze skin tissue.
- Never allow refrigerant R-134a gas to escape in quantity in an occupied space. It will displace the oxygen needed to support life.
- Never use a torch in an atmosphere containing R-134a gas. R-134a is non-toxic at all normal conditions, but it decomposes when exposed to high temperatures such as a torch flame. During decomposition it releases irritating and toxic gasses (as described in the MSDS sheet from the manufacturer). Decomposition products are hydrofluoric acid, carbon dioxide and water.
Failure to follow these instructions may result in serious personal injury.
WARNING: Use extreme care and observe all safety and service precautions related to the use of refrigerants as outlined on refrigerant tank and on recovery and charging equipment. Failure to follow these instructions may result in serious personal injury.
NOTICE: To avoid damaging the vehicle or Air Conditioning (A/C) components, the following precautions must be observed.
- The A/C refrigerant of all vehicles must be identified and analyzed prior to refrigerant charging. Failure to do so can contaminate the shop bulk refrigerant and other vehicles.
- Do not add R-12 refrigerant to an A/C system that requires the use of R-134a refrigerant. These 2 types of refrigerant must never be mixed. Doing so can damage the A/C system.
- Charge the A/C system with R-134a refrigerant gas while the engine is running only at the low-pressure side to prevent refrigerant slugging from damaging the A/C compressor.
- Use only R-134a refrigerant. Due to environmental concerns, when the A/C system is drained, the refrigerant must be collected using refrigerant recovery/recycling equipment. Federal, State/Provincial and/or local laws REQUIRE that R-134a be recovered into appropriate recovery equipment and the process be conducted by qualified technicians who have been certified by an approved organization, such as ASE or Mobile Air Conditioning Society (MACS). Use of a recovery machine dedicated to R-134a is necessary to reduce the possibility of oil and refrigerant incompatibility concerns. Refer to the instructions provided by the equipment manufacturer when removing refrigerant from or charging the A/C system.
- Refrigerant R-134a must not be mixed with air for leak testing or used with air for any other purpose above atmospheric pressure. R-134a is combustible when mixed with high concentrations of air and higher pressures.
- A number of manufacturers are producing refrigerant products that are described as direct substitutes for refrigerant R-134a. The use of any unauthorized substitute refrigerant can severely damage the A/C components. If repair is required, use only new or recycled refrigerant R-134a.
NOTICE: To avoid contamination of the Air Conditioning (A/C) system, the following precautions must be observed.
- Never open or loosen a connection before recovering the refrigerant.
- When loosening a connection, if any residual pressure is evident, allow it to leak out before opening the fitting.
- Evacuate a system that has been opened to install a new component or one that has discharged through leakage before charging.
- Seal open fittings with a cap or plug immediately after disconnecting a component from the system.
- Clean the outside of the fittings thoroughly before disconnecting a component from the system.
- Do not remove the sealing caps from a new component until ready to install.
- Refrigerant oil will absorb moisture from the atmosphere if left uncapped. Do not open an oil container until ready to use and install the cap immediately after using. Store the oil in a clean, moisture-free container.
- Install a new O-ring seal before connecting an open fitting. Coat the fitting and O-ring seal with PAG oil before connecting.
- When installing a refrigerant line, avoid sharp bends. Position the line away from the exhaust or any sharp edges that can chafe the line.
- Tighten threaded fittings only to specifications. The steel and aluminum fittings used in the refrigerant system will not tolerate overtightening.
- When disconnecting a fitting, use a wrench on both halves of the fitting to prevent twisting of the refrigerant lines or tubes.
- Do not open a refrigerant system or uncap a new component unless it is as close as possible to room temperature. This will prevent condensation from forming inside a component that is cooler than the surrounding air.
The system components are the following:
- A/C compressor
- A/C compressor clutch assembly
- A/C condenser core
- A/C evaporator core
- Suction accumulator
- Connecting refrigerant lines
- A/C evaporator core orifice
- A/C cycling switch
- High-pressure cutoff switch (5.4L and 6.8L)
- Dual-function pressure switch (6.4L diesel)
- Heater core and evaporator core housing
- HVAC module - Electronic Manual Temperature Control (EMTC) or HVAC module - Dual Automatic Temperature Control (DATC)
- Blower switch (EMTC systems)
- Temperature blend door actuators
- Floor/defrost/panel door actuator
- Air inlet door actuator
- Blower motor resistor or speed control module
- Blower motor
- Ambient temperature sensor
- In-vehicle temperature sensor
- Solar radiation sensor
Electronic Manual Temperature Control (EMTC) System
The EMTC system heats or cools the vehicle depending on the EMTC control panel selection.
- The HVAC module - EMTC control panel selections determine heating or cooling, air distribution and enables blower motor operation.
- The temperature control setting determines the air temperature.
- The blower motor switch varies the blower motor speed.
- During A/C operation the system also reduces the relative humidity of the air.
The EMTC system operation is determined by the settings on the climate control module. The EMTC system is composed of the HVAC module - EMTC, blower motor resistor, mode door actuator, air inlet door actuator and temperature blend door actuator to control the various functions.
The blower motor switch:
- sets the blower motor speed.
- directs the blower motor path to ground through the blower motor resistor to allow blower motor operation in LO, MED-LO and MED-HI.
- directs the blower motor path directly to ground, bypassing the blower motor resistor, to allow blower motor operation in HI.
The A/C request button:
- can command the A/C compressor ON when the function selector switch is in PANEL, FLOOR/PANEL, FLOOR/DEFROST and FLOOR when the A/C request switch is pressed. Indicator illuminates when A/C request switch is toggled ON.
- is inoperative in MAX A/C, OFF and DEFROST.
- indicator illuminates when the function selector switch is in MAX A/C and cannot be toggled.
- indicator does not illuminate in OFF and cannot be toggled.
- indicator does not illuminate in DEFROST but can be toggled ON or OFF. The A/C compressor will operate regardless of indicator status if the outside air temperature is above 6°C (43°F).
- is serviced only with the HVAC module - EMTC.
The function selector:
- selects airflow direction.
- is serviced only with the HVAC module - EMTC.
The temperature selector:
- selects full warm and full cool as well as blended outlet temperatures.
The air recirculation button:
- selects either recirculated or outside air source.
- recirculates air in any mode except DEFROST, if requested.
- is disabled in MAX A/C or OFF mode where recirculated air only is used.
- is disabled in DEFROST mode where outside air only is used.
- is serviced only with the HVAC module - EMTC.
The EMTC module also includes:
- a heated mirror button. Refer to Mirrors.
- heated seat controls. Refer to Seats.
Dual Automatic Temperature Control (DATC) System
The DATC system maintains the selected vehicle interior temperature by heating and/or cooling the air.
- During A/C operation the system also reduces the relative humidity of the air.
- The driver may override the automatic mode of operation.
- The temperature control setting determines the desired air temperature.
- The blower motor control override button varies the blower motor speed.
- The driver side and passenger side temperature settings can be individually controlled.
The DATC system operation is determined by the settings on the HVAC module - DATC. The DATC system automatically maintains a selected temperature for vehicle interior comfort. The DATC system is composed of the HVAC module - DATC, blower motor speed control, mode door actuator, air inlet door actuator, driver and passenger temperature blend door actuators, in-vehicle temperature sensor, ambient temperature sensor and solar radiation sensor to control the various functions.
When the DATC module is set to AUTO:
- the air distribution direction, blower motor speed and A/C compressor operation are automatically controlled based on the temperature(s) selected.
The HVAC module - DATC manual override settings:
- allow the air distribution direction to be manually selected.
- allow the blower motor speed to be manually selected.
- allow recirculation mode to be manually selected in all modes except DEFROST. The A/C request can be cancelled by pressing the A/C request switch, turning the indicator OFF.
- allow A/C compressor operation to be manually selected except in DEFROST.
The HVAC module - DATC also includes:
- a heated mirror button, refer to Mirrors.
- heated seat controls, refer to Seats.
External Temperature Display
The external temperature is displayed when the EXT button is pressed. The external temperature display will update when the vehicle has been driven above 35 kph (22 mph) for a period of time.
Auxiliary Electric Heater
An electric heater is available as optional equipment on diesel vehicles. The electronic heater assembly contains the Auxiliary Heater Control Module (AHCM) and element, and is located in the HVAC immediately downstream of the heater core.
Power is supplied to the AHCM element through a fused cable connected directly to the positive battery terminal with an in-line connection at the dash panel heater tube opening. Ground is supplied to the electric heater element through a ground cable connected directly to the negative battery terminal with an in-line connection at the dash panel heater tube opening. The AHCM is activated by a Medium Speed Controller Area Network (MS-CAN) message from the HVAC module - EMTC or HVAC module - DATC. The MS-CAN message is converted to a HS-CAN message by the Instrument Cluster (IC) module and is then detected by the AHCM.
The electric heater will be activated if all of the following conditions are met:
- The ignition switch is in the RUN/START position
- The engine is operating at greater than 500 rpm
- Any ON mode is selected on the HVAC module - EMTC or HVAC module - DATC
- The temperature set point is greater than 80% of the highest setting (EMTC only, DATC uses software algorithm based on interior temp and set point)
- The engine coolant temperature is less than 85°C (185°F)
- No alternator faults have been recorded and alternator is not at full capacity
The AHCM will be deactivated if any of the following conditions are met:
- The ignition switch is in the OFF or ACC position
- The engine coolant temperature is greater than 85°C (185°F)
- An alternator fault has been detected or the alternator is fully loaded due to external electrical loads
- The engine is operating at less than 500 rpm
- The auxiliary heat request is NO from the HVAC module - EMTC or HVAC module - DATC
System Airflow Description - Electronic Manual Temperature Control (EMTC) System
Max A/C
When MAX A/C is selected:
- the air inlet door actuator closes off outside air and admits only recirculated air.
- the recirc button is disabled and the indicator is illuminated.
- the floor/defrost/panel door directs airflow to the instrument panel A/C registers.
- blended air temperature is available.
- the A/C request button is illuminated and will be disabled.
- the A/C compressor will operate if the outside temperature is above approximately 1°C (30°F).
- the blower motor is ON.
PANEL
When PANEL is selected:
- the recirc request button is enabled. If the recirc request button is selected (indicator ON), the air inlet door actuator closes off outside air from entering the passenger compartment. If the recirc request button is not selected (indicator OFF), the air inlet door actuator admits only outside air into the passenger compartment.
- the floor/defrost/panel door directs airflow to the instrument panel A/C registers.
- blended air temperature is available.
- the A/C request button is enabled. The A/C compressor will operate and the indicator will illuminate if the A/C request button is selected and the outside temperature is above approximately 1°C (30°F).
- the blower motor is ON.
PANEL/FLOOR
When PANEL/FLOOR is selected:
- the recirc request button is enabled. If the recirc request button is selected (indicator ON), the air inlet door actuator closes off outside air from entering the passenger compartment. If the recirc request button is not selected (indicator OFF), the air inlet door actuator admits only outside air into the passenger compartment.
- the floor/defrost/panel door directs airflow to the floor duct and the instrument panel A/C registers. A small amount of airflow from the side window demisters and defrost duct will be present.
- blended air temperature is available.
- the A/C request button is enabled. The A/C compressor will operate and the indicator will illuminate if the A/C request button is selected and the outside temperature is above approximately 1°C (30°F).
- the blower motor is ON.
OFF
When OFF is selected:
- the recirc request button is disabled.
- the air inlet door actuator closes off outside air and admits only recirculated air.
- the A/C request button is disabled.
- the blower motor is OFF.
FLOOR
When FLOOR is selected:
- the recirc request button is enabled. If the recirc request button is selected (indicator ON), the air inlet door actuator closes off outside air from entering the passenger compartment. If the recirc request button is not selected (indicator OFF), the air inlet door actuator admits only outside air into the passenger compartment.
- the floor/defrost/panel door directs airflow to the floor duct. A small amount of airflow from the defroster duct and side window demisters will be present.
- blended air temperature is available.
- the A/C request button is enabled. The A/C compressor will operate and the indicator will illuminate if the A/C request button is selected and the outside temperature is above approximately 1°C (30°F).
- the blower motor is ON.
FLOOR/DEFROST
When the FLOOR/DEFROST is selected:
- the recirc request button is enabled. If the recirc request button is selected (indicator ON), the air inlet door actuator closes off outside air from entering the passenger compartment. If the recirc request button is not selected (indicator OFF), the air inlet door actuator admits only outside air into the passenger compartment.
- the floor/defrost/panel door directs airflow to the floor duct, the defroster duct and the side window demisters.
- blended air temperature is available.
- the A/C request button will indicate the last status and the indicator can be toggled. To reduce fogging, the A/C compressor will operate automatically, regardless of indicator status, if the outside temperature is above approximately 1°C (30°F).
- the blower motor is ON.
DEFROST
When DEFROST is selected:
- the air inlet door actuator opens, admitting only outside air into the passenger compartment.
- the floor/defrost/panel door directs airflow to the defroster duct and side window demisters. A small amount of airflow from the floor duct will be present.
- blended air temperature is available.
- the A/C request button will indicate the last status and the indicator can be toggled. To reduce fogging, the A/C compressor will operate automatically, regardless of indicator status, if the outside temperature is above approximately 6°C (43°F).
- the blower motor is ON.
System Airflow Description - Dual Automatic Temperature Control (DATC) System
AUTO
When AUTO is selected:
- the temperature control setting is manually set to the desired setting.
- the air inlet door actuator is automatically controlled by the HVAC module - DATC, based on the temperature setting.
- the mode door actuators are automatically controlled by the HVAC module - DATC, based on the temperature setting.
- the A/C compressor is automatically controlled by the HVAC module - DATC based on the temperature setting. The A/C compressor will not operate if the outside temperature is below approximately 1°C (30°F).
- the A/C request button or the recirc request button, if pressed, will transfer the system to semi-auto operation.
- the blower motor is ON. The blower motor speed is automatically controlled by the HVAC module - DATC based on the temperature setting, but can be manually overridden.
OFF
When OFF is selected:
- the recirc request button is disabled.
- the air inlet door actuator closes off outside air and admits only recirculated air.
- the floor/defrost/panel door actuator is in the DEFROST position.
- the A/C request button is disabled.
- the blower motor is OFF.
PANEL
When PANEL is selected:
- the recirc request button is enabled. If the recirc request button is selected (indicator ON), the air inlet door actuator closes off outside air from entering the passenger compartment. If the recirc request button is not selected (indicator OFF), the air inlet door actuator admits only outside air into the passenger compartment.
- the floor/defrost/panel door directs airflow to the instrument panel A/C registers.
- blended air temperature is available. Only when A/C compressor operation has been selected by pressing the A/C request button (indicator ON), can the airflow temperature be cooled below the outside air temperature.
- the A/C request button is enabled. The A/C compressor will operate and the indicator will illuminate if the A/C request button is selected and the outside temperature is above approximately 1°C (30°F).
- the blower motor is ON.
PANEL/FLOOR
When PANEL/FLOOR is selected:
- the recirc request button is enabled. If the recirc request button is selected (indicator ON), the air inlet door actuator closes off outside air from entering the passenger compartment. If the recirc request button is not selected (indicator OFF), the air inlet door actuator admits only outside air into the passenger compartment.
- the floor/defrost/panel door directs airflow to the floor duct and the instrument panel A/C registers. A small amount of airflow from the side window demisters and defrost duct will be present.
- blended air temperature is available. Only when A/C compressor operation has been selected by pressing the A/C request button (indicator ON), can the airflow temperature be cooled below the outside air temperature.
- the A/C request button is enabled. The A/C compressor will operate and the indicator will illuminate if the A/C request button is selected and the outside temperature is above approximately 1°C (30°F).
- the blower motor is ON.
FLOOR
When FLOOR is selected:
- the recirc request button is enabled. If the recirc request button is selected (indicator ON), the air inlet door actuator closes off outside air from entering the passenger compartment. If the recirc request button is not selected (indicator OFF), the air inlet door actuator admits only outside air into the passenger compartment.
- the floor/defrost/panel door directs airflow to the floor duct. A small amount of airflow from the defroster duct and side window demisters will be present.
- blended air temperature is available. Only when A/C compressor operation has been selected by pressing the A/C request button (indicator ON), can the airflow temperature be cooled below the outside air temperature.
- the A/C request button is enabled. The A/C compressor will operate and the indicator will illuminate if the A/C request button is selected and the outside temperature is above approximately 1°C (30°F).
- the blower motor is ON.
FLOOR/DEFROST
When the FLOOR/DEFROST is selected:
- the recirc request button is enabled. If the recirc request button is selected (indicator ON), the air inlet door actuator closes off outside air from entering the passenger compartment. If the recirc request button is not selected (indicator OFF), the air inlet door actuator admits only outside air into the passenger compartment.
- the floor/defrost/panel door directs airflow to the floor duct, the defroster duct and the side window demisters.
- blended air temperature is available.
- the A/C request button is enabled. The A/C compressor will operate automatically and the indicator will illuminate if the A/C request button is selected and the outside temperature is above approximately 1°C (30°F).
- the blower motor is ON.
DEFROST
When DEFROST is selected:
- the recirc request button and indicator is disabled. Regardless of button and indicator status, the air inlet door actuator admits only outside air into the passenger compartment.
- the floor/defrost/panel door directs airflow to the defroster duct and side window demisters. A small amount of airflow from the floor duct will be present.
- blended air temperature is available.
- the A/C request button will indicate the last status and the indicator can be toggled. To reduce fogging, the A/C compressor will operate automatically, regardless of indicator status, if the outside temperature is above approximately 1°C (30°F).
- the blower motor is ON.