Climate Control System
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.
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 the engine 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 law REQUIRES 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 MACS, ASI). 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:
- 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 pressure cutoff switch
- A/C cycling switch
- Heater core and evaporator core housing
- HVAC module
- Temperature blend door actuators
- Floor/defrost/panel door actuator
- Air inlet door actuator
- Blower motor speed control
- Blower motor
- Ambient temperature sensor
- In-vehicle temperature sensor
- Solar radiation sensor
HVAC Module Description
The Dual Automatic Temperature Control (DATC) system automatically maintains a selected temperature for vehicle interior comfort and regulates the volume of airflow between the instrument panel registers, floor ducts, windshield defroster nozzle and side window demisters. The system will automatically select between fresh and recirculated air with an optional manual override. The DATC system will also include a manual A/C override, blower speed override and airflow direction overrides.
The dual temperature zone feature provides the driver and the front seat passenger with their own independent temperature set points. The DATC system provides both the driver and front seat passenger with their selected temperature for interior comfort. In situations where the difference between the driver and the front seat passenger set points are very large, the HVAC module will tend to favor the driver's setting and make the front seat passenger as comfortable as possible.
The driver and front seat passenger will not have independent air distribution mode or fan controls so the system is dual temperature only. In some cases, the passenger temperature set point may influence the air distribution mode or blower speed in automatic mode.
External Temperature Display
The external temperature is displayed when the EXT button is pressed. While the actual external temperature can vary continuously, the value that is displayed will update at a specific rate depending on whether or not the engine is "hot" and whether or not the vehicle is moving.
When the external temperature is rising, the display will update slowly. Updates (when the actual external temperature is higher than currently displayed value) will be limited to 0.6°C (1°F) every 20 seconds while the vehicle is moving at 40 km/h (25 mph) or greater for more than 90 seconds, or 0.6°C (1°F) every 20 minutes if the vehicle is not moving at this speed. This is to prevent the heat from the engine compartment from affecting the accuracy of the display.
When the external temperature is dropping, the display will update quickly.
Updates (when the actual external temperature is lower than currently displayed value) will only be limited to 0.6°C (1°F) every 2 seconds (regardless of vehicle speed). Consequently, the display will essentially follow the drop experienced by the external temperature thermistor.
System Airflow
AUTO
When AUTO is selected:
- the temperature control setting(s) is manually set to the desired setting(s).
- the air inlet door actuator is automatically controlled by the HVAC module, based on the temperature setting(s), but can be manually overridden by selecting the recirculation button.
- the panel/defrost and floor door actuators are automatically controlled by the HVAC module based on the temperature setting(s), but can be manually overridden by selecting any of the air distribution buttons.
- the A/C compressor is automatically controlled by the HVAC module based on the temperature setting(s), but can be manually overridden by selecting the A/C button. The A/C compressor will not operate if the outside temperature is lower than approximately 2°C (35°F).
- the blower motor is on. The blower motor speed is automatically controlled by the HVAC module based on the temperature setting(s), but can be manually overridden by adjusting the blower speed rocker button.
OFF
When OFF is selected:
- the air inlet door actuator positions the air inlet door to close off outside air from entering the passenger compartment.
- the floor door actuator positions the floor door in the open position, the panel/defrost door actuator positions the panel/defrost door in the panel position.
- the blower motor and A/C compressor are 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 positions the air inlet door to close off outside air from entering the passenger compartment. If the Recirc request button is not selected (indicator OFF), the air inlet door actuator positions the air inlet door to admit only outside air into the passenger compartment.
- the floor door actuator positions the floor door in the closed position, and the panel/defrost door actuator positions the panel/defrost door to direct airflow to the instrument panel A/C registers. The system will allow some airflow through the floor ducts.
- temperature control can be adjusted by directing the airflow through and around the heater core. Only when the A/C compressor operation has been selected by pressing the A/C request switch (indicator ON) can the airflow temperature be cooled below that of the ambient (outside) air temperature.
- the A/C request button is enabled. When the A/C request button is selected (indicator ON), the A/C compressor will operate if the outside air temperature is above approximately 2°C (35°F). When the A/C request button is not selected (indicator OFF), the A/C compressor will not operate and the air cannot be cooled below the outside temperature.
- 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 positions the air inlet door to close off outside air from entering the passenger compartment. If the Recirc request button is not selected (indicator OFF), the air inlet door actuator positions the air inlet door to admit only outside air into the passenger compartment.
- the floor door actuator positions the floor door in the partially open position to direct partial airflow to the floor duct, and the panel/defrost door actuator positions the panel/defrost door to direct airflow to the instrument panel A/C registers.
- temperature control can be adjusted by directing the airflow through and around the heater core. Only when the A/C compressor operation has been selected by pressing the A/C request switch (indicator ON) can the airflow temperature be cooled below that of the ambient (outside) air temperature.
- the A/C request button is enabled. When the A/C request button is selected (indicator ON), the A/C compressor will operate if the outside air temperature is above approximately 2°C (35°F). When the A/C request button is not selected (indicator OFF), the A/C compressor will not operate and the air cannot be cooled below the outside temperature.
- 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 positions the air inlet door to close off outside air from entering the passenger compartment. If the Recirc request button is not selected (indicator OFF), the air inlet door actuator positions the air inlet door to admit only outside air into the passenger compartment. The HVAC module will automatically revert to the outside air position after approximately 4 minutes to prevent window fogging.
- the floor door actuator positions the floor door in the open position, and the panel/defrost door actuator positions the panel/defrost door in the defrost position. A small amount of airflow from the defrost ducts and demisters will be present.
- temperature control can be adjusted by directing the airflow through and around the heater core. Only when the A/C compressor operation has been selected by pressing the A/C request switch (indicator ON), can the airflow temperature be cooled below that of the ambient (outside) air temperature.
- the A/C request button is enabled. When the A/C request button is selected (indicator ON), the A/C compressor will operate if the outside air temperature is above approximately 2°C (35°F). When the A/C request button is not selected (indicator OFF), the A/C compressor will not operate and the air cannot be cooled below the outside temperature.
- the blower motor is ON.
FLOOR/DEFROST
When FLOOR/DEFROST is selected:
- the Recirc request button is enabled. If the Recirc request button is selected (indicator ON), the air inlet door actuator positions the air inlet door to close off outside air from entering the passenger compartment. If the Recirc request button is not selected (indicator OFF), the air inlet door actuator positions the air inlet door to admit only outside air into the passenger compartment. The HVAC module will automatically revert to the outside air position after approximately 4 minutes to prevent window fogging.
- the floor door actuator positions the floor door in the partially open position to direct partial airflow to the floor duct, and the panel/defrost door actuator positions the panel/defrost door to direct airflow to the defrost duct and side window demisters.
- temperature control can be adjusted by directing the airflow through and around the heater core.
- the A/C request button is disabled.
- the A/C compressor will operate automatically if the outside temperature is above 2°C (35°F).
- the blower motor is ON.
DEFROST
When DEFROST is selected:
- the Recirc request button is disabled. The air inlet door actuator positions the air inlet door to admit only outside air into the passenger compartment.
- the floor door actuator positions the floor door in the closed position, and the panel/defrost door actuator positions the panel/defrost door to direct airflow to the defrost duct and side window demisters.
- temperature control can be adjusted by directing the airflow through and around the heater core.
- the A/C request button is disabled.
- the A/C compressor will operate automatically if the outside temperature is above 2°C (35°F).
- the blower motor is ON.