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.

CAUTION:
- 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 ASE, MACS, HRAI, etc. 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.

- 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 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 mineral 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 electronic manual temperature control (EMTC) system heats or cools the vehicle depending on the EMTC control panel selection.
- The 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 dual-zone electronic automatic temperature control (EATC) 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 air temperature.
- The blower motor control override buttons vary the blower motor speed.
- The driver side and passenger side temperature settings can be individually controlled.

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
- EMTC or EATC module
- 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
- Evaporator discharge air temperature sensor

Electronic Manual Temperature Control (EMTC) System
The EMTC system heats or cools the vehicle depending on the EMTC control panel selection.
- The 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. To control the various functions, the EMTC system is composed of the following:
- EMTC module
- Blower motor resistor
- Mode door actuator
- Air inlet door actuator
- Temperature blend door actuator

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 EMTC module.

The function selector:
- selects airflow direction.
- is serviced only with the EMTC module.

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 EMTC module.

The EMTC module also includes:
- a rear window defrost button. Refer to Windows.

Electronic Automatic Temperature Control (EATC) System
The dual-zone EATC 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 EATC system operation is determined by the settings on the EATC module. The EATC system automatically maintains a selected temperature for vehicle interior comfort. To control the various functions, the EATC system is composed of the following:
- EATC module
- 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
- Solar radiation sensor
- Evaporator temperature sensor

When the EATC 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 EATC module 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.
- select the auxiliary blower motor speed.
- select the auxiliary airflow mode/temperature.

The EATC module also includes:
- a rear window DEFROST button. Refer to Windows.
- heated seat controls. Refer to Seats.

Auxiliary Climate Control System
An auxiliary climate control system is available as optional equipment. The auxiliary climate control system operation is determined by the settings on the front or rear auxiliary climate control assembly. The auxiliary climate control assemblies include a blower motor switch and temperature control/air distribution mode knob, neither of which can be individually serviced.

Auxiliary blower motor operation is enabled when the EMTC or EATC is in any mode except OFF. The auxiliary system air can be cooled below interior air temperature only when A/C compressor operation has been requested by the settings of the climate control assembly of the base (front) system. The auxiliary system air can be heated at any time.

The front auxiliary climate controls:
- are built into the dual-zone EMTC or EATC module. The blower motor speed can be set to OFF, LO, MED LO, MED HI or HI by pressing the auxiliary blower FAN button either right (higher) or left (lower). The temperature/airflow mode can be adjusted by pressing the rear button either right (warm/floor) or left (cool/panel). If the front (main) driver side temperature is set to full COOL or full HEAT, the auxiliary temperature will be set to the same as the driver and cannot be changed. When the front auxiliary REAR button is depressed, all control of the auxiliary climate control system functions are then transferred to the rear auxiliary climate control assembly and the auxiliary temperature can be fully independently controlled.

The rear auxiliary climate control assembly:
- blower motor switch controls the auxiliary blower motor speed only when the front auxiliary climate control assembly blower motor switch is set to REAR. The blower motor speed can be set to OFF, LO, MED LO, MED HI or HI.
- temperature/airflow mode control switch is a potentiometer that outputs a variable voltage to the auxiliary temperature blend door actuator and auxiliary mode door actuator to set the position of the auxiliary temperature blend and mode doors only when the front auxiliary climate control assembly blower motor switch is set to REAR. When A/C compressor operation has not been initiated (A/C compressor commanded on) by the EMTC or EATC module (as equipped), the auxiliary climate control system cannot cool the air below that of the interior air temperature.