Part 1

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 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 Automotive Service Excellence (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 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 absorbs 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 does 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 prevents condensation from forming inside a component that is cooler than the surrounding air.


The system consists of the following components:

- A/C compressor
- A/C compressor clutch assembly
- A/C condenser core
- A/C evaporator core
- Receiver/drier
- Connecting refrigerant lines
- Thermostatic Expansion Valve (TXV)
- A/C pressure transducer
- Heater core and evaporator core housing
- HVAC module
- Front Controls Interface Module (FCIM) (vehicles equipped with navigation systems)
- Front Display Interface Module (FDIM)
- Air inlet mode door actuator
- Defrost/panel/floor mode door actuator
- Temperature blend door actuator(s)
- Blower motor resistor (Electronic Manual Temperature Control (EMTC) systems only)
- Blower motor speed control (Dual Automatic Temperature Control (DATC) systems only)
- Blower motor
- In-vehicle temperature and humidity sensor
- Autolamp/sunload sensor ( DATC systems only)
- Evaporator temperature sensor (serviced only with the heater core and evaporator core housing)

External Temperature Display

The ambient air temperature sensor is monitored by the PCM. The PCM sends the raw value through the High Speed Controller Area Network (HS-CAN) to the Body Control Module (BCM), and from the BCM through the Medium Speed Controller Area Network (MS-CAN) to the HVAC module. The HVAC module filters and stabilizes the value and sends it to the FDIM to display the temperature, through the MS-CAN.

While the actual external temperature can vary continuously, the value that is displayed updates 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 updates slowly.

Updates (when the actual external temperature is higher than currently displayed value) is limited to 0.6°C (1°F) every 20 seconds while the vehicle is moving at greater than 24 km/h (15 mph) 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 updates quickly.

Updates (when the actual external temperature is lower than currently displayed value) are limited to 0.6°C (1°F) every 2 seconds (regardless of vehicle speed). Consequently the display essentially follows the drop experienced by the external temperature thermistor.

Electronic Manual Temperature Control (EMTC) System

System Operation

The EMTC system heats or cools the vehicle depending on the HVAC module control panel selection.

- The control panel selection determines heating or cooling, air distribution and enables blower motor operation.
- The temperature control setting determines the outlet air temperature.
- The blower motor switch varies the blower motor speed.
- During A/C operation, the system reduces the relative humidity of the air inside the vehicle.

Remote Start System Behavior - Message Center Set to Auto

This vehicle is equipped with a remote start feature. In addition to being able to start the vehicle remotely, the remote start feature also utilizes other vehicle systems to increase the level of comfort to the vehicle occupants upon entering the vehicle. For additional information on the remote start feature and the other vehicle systems it utilizes, refer to Starting System Description and Operation.

When the remote start feature is used, the climate control system automatically sets certain parameters in an attempt to achieve a comfortable cabin temperature. These parameters are set based on outside air temperature. During remote start, the outside air temperature is continually evaluated and HVAC system behavior can change if the outside air changes between cold, moderate and warm temperatures.

For cold ambient air temperatures (below 0°C (32°F)):

- the airflow mode is set to FLOOR/DEFROST if Front Defrost is set to Off in the message center.
- the airflow mode is set to DEFROST if Front Defrost is set to Auto in the message center.
- the temperature is set to full HOT.
- the blower speed is set to HIGH.
- the air inlet mode is set to fresh air.
- A/C is set to OFF.

For moderate ambient air temperatures (between 0°C (32°F) and 27°C (80°F)):

- the airflow mode is set to the last user setting.
- the temperature is set to the last user setting.
- the blower speed is set to the last user setting.
- the air inlet mode is set to the last user setting.
- A/C is set to the last user setting.

For warm ambient air temperatures (above 27°C (80°F)):

- the airflow mode is set to MAX A/C.
- the temperature is set to full COOL.
- the blower speed is set to HIGH.
- the air inlet mode is set to RECIRC.
- A/C is set to ON.

Remote Start System Behavior - Message Center Set to Last User Settings

This vehicle is equipped with a remote start feature. In addition to being able to start the vehicle remotely, the remote start feature also utilizes other vehicle systems to increase the level of comfort to the vehicle occupants upon entering the vehicle. For additional information on the remote start feature and the other vehicle systems it utilizes, refer to Starting System Description and Operation.

When the remote start feature is used, the climate control system automatically sets certain parameters in an attempt to achieve a comfortable cabin temperature. These parameters are set based on outside air temperature. During remote start, the outside air temperature is continually evaluated and HVAC system behavior can change if the outside air changes between cold, moderate and warm temperatures.

For additional information regarding the message center, refer to Instrumentation, Message Center, and Warning Chimes Description and Operation.

When Heater - A/C is set to Last User Settings in the message center, the remote start sets the climate control system to the following settings.

- For cold ambient air temperatures as determined by the HVAC module:
- the airflow mode is set to the last user setting if Front Defrost is set to Off in the message center.
- the airflow mode is set to DEFROST if Front Defrost is set to Auto in the message center.
- the temperature is set to the last user setting.
- the blower speed is set to the last user setting.
- the air inlet mode is set to the last user setting.
- A/C is set to the last user setting.

- For moderate and warm ambient air temperatures as determined by the HVAC module:
- the airflow mode is set to the last user setting.
- the temperature is set to the last user setting.
- the blower speed is set to the last user setting.
- the air inlet mode is set to the last user setting.
- A/C is set to the last user setting.

System Airflow and Mode Description

Max A/C

When MAX A/C is selected:

- the air inlet door closes, preventing outside air and admits only recirculated air.
- the RECIRC indicator is illuminated (RECIRC forced on).
- the mode doors direct airflow to the instrument panel A/C registers.
- blended air temperature is available.
- the A/C request button is illuminated.
- the A/C compressor operates if the outside temperature is above approximately 0°C (32°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 closes, preventing outside air from entering the passenger compartment. If the RECIRC 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 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 operates and the indicator illuminates if the A/C request button is selected and the outside temperature is above approximately 0°C (32°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 closes, preventing outside air from entering the passenger compartment. If the RECIRC 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 A/C 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 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 operates and the indicator illuminates if the A/C request button is selected and the outside temperature is above approximately 0°C (32°F).
- the blower motor is on.

OFF

When OFF is selected:

- the air inlet door closes, preventing outside air and allowing only recirculated air.
- the blower motor is off.