Auxiliary Climate Control
Auxiliary Climate Control
Component Location
Overview
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 HVAC (Heating, Ventilation, and Air Conditioning) system is in any mode except OFF. The auxiliary system air can be cooled below interior air temperature only when A/C (Air Conditioning) 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.
System Operation
System Diagram
Network Message Chart
Module Network Input Messages - FCIM (Front Controls Interface Module)
Module Network Input Messages - APIM (Accessory Protocol Interface Module)
Module Network Input Messages - HVAC (Heating, Ventilation, and Air Conditioning) Module
Auxiliary Climate Controls
The Front Auxiliary Climate Controls
The blower motor speed can be set to OFF, LO, MED-LO, MED-HI or HI by pressing the auxiliary blower FAN "+" or "-" button. The temperature/airflow mode can be adjusted by pressing the rear TEMPERATURE "+" or "-" button. 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 Controls
The 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.
The temperature control is a potentiometer that tells the HVAC (Heating, Ventilation, and Air Conditioning) module the desired temperature setting. The HVAC module then moves the mode door actuator to the appropriate position. When A/C (Air Conditioning) compressor operation has not been initiated ( A/C (Air Conditioning) compressor commanded on) by the HVAC (Heating, Ventilation, and Air Conditioning) module (as equipped), the auxiliary climate control system cannot cool the air below that of the interior air temperature.
The airflow mode control switches tell the HVAC (Heating, Ventilation, and Air Conditioning) module the desired airflow mode setting. The HVAC (Heating, Ventilation, and Air Conditioning) module then moves the mode door actuator to the appropriate position.
REAR LOCK
Control for the auxiliary climate control system can be controlled by the front or rear climate controls. When REAR CONTROL is selected on the front auxiliary climate controls, the rear auxiliary climate controls can be used. When REAR CONTROL is not selected, REAR LOCK is illuminated in the rear auxiliary climate controls. The rear auxiliary climate controls does not work when the REAR LOCK indicator is illuminated and only the front auxiliary climate controls may be used.
Auxiliary System Airflow
The auxiliary climate control system has the following features:
- A vertical air distribution duct supplies air to the integral headliner air distribution duct. Airflow is then directed to the passengers through adjustable registers. The heater floor duct supplies air to a fixed register, which is integral to the side trim panel.
- The auxiliary blower motor recirculates the air inside the vehicle. Outside air is not available to the auxiliary climate control system.
- Air is cooled and dehumidified by the auxiliary evaporator core only if the main (front) climate control assembly is adjusted to a position that requires A/C (Air Conditioning) compressor operation.
- The temperature blend door and the airflow mode door are controlled by electric actuator motors.
- Movement of the auxiliary temperature/mode control between COOL and WARM causes a corresponding movement of the temperature blend door to mix air flowing through and around the auxiliary heater core. Selection of the auxiliary mode control buttons causes a corresponding movement of the mode door to direct airflow to the ROOF and FLOOR positions.
Component Description
Rear Auxiliary Climate Control Assembly
The vehicle has dual climate controls for the auxiliary unit. The front controls are built into the FCIM (Front Controls Interface Module), and can control the auxiliary unit by means of a temperature selection button and blower speed control, or can transfer control to the rear auxiliary climate control assembly. The rear auxiliary climate control has separate controls for blower speed, temperature blend and airflow mode.
Auxiliary Mode Door Actuator
The auxiliary mode door actuator moves the auxiliary mode door on command from the HVAC (Heating, Ventilation, and Air Conditioning) module based on input from either the front or rear auxiliary climate controls.
The auxiliary mode door actuator contains a reversible electric motor and potentiometer. The potentiometer allows the HVAC (Heating, Ventilation, and Air Conditioning) module to monitor the position of the auxiliary mode door. The potentiometer circuit consists of a 5-volt reference signal connected to one end of a variable resistor, and a signal ground connected to the other. A signal circuit is connected to a contact wiper, which is driven along the variable resistor by the actuator shaft. The signal to the HVAC (Heating, Ventilation, and Air Conditioning) module from the contact wiper indicates the position of the airflow mode door.
Auxiliary Temperature Blend Door Actuator
The auxiliary temperature blend door actuator moves the auxiliary temperature blend door on command from the HVAC (Heating, Ventilation, and Air Conditioning) module based on input from either the front or rear auxiliary climate controls.
The auxiliary temperature blend door actuator contains a reversible electric motor and potentiometer. The potentiometer allows the HVAC (Heating, Ventilation, and Air Conditioning) module to monitor the position of the auxiliary temperature blend door. The potentiometer circuit consists of a 5-volt reference signal connected to one end of a variable resistor, and a signal ground connected to the other. A signal circuit is connected to a contact wiper, which is driven along the variable resistor by the actuator shaft. The signal to the HVAC (Heating, Ventilation, and Air Conditioning) module from the contact wiper indicates the position of the airflow temperature blend door.
Auxiliary Blower Motor Speed Control
The auxiliary blower motor speed control controls the auxiliary blower motor speed, based on input from either the front or rear auxiliary climate controls by converting low power signals from the HVAC (Heating, Ventilation, and Air Conditioning) module to a high current, variable ground feed for the auxiliary blower motor.
Auxiliary Blower Motor
The auxiliary climate control system contains a blower motor, which is controlled by either the front or rear auxiliary climate controls.
Auxiliary Evaporator Core
The auxiliary climate control system uses an evaporator core, which cools and dehumidifies the airflow from the auxiliary blower motor when the A/C (Air Conditioning) compressor is operating. All airflow from the blower motor passes through the evaporator core.
Auxiliary Heater Core
The heater core consists of fins and tubes arranged to extract heat from the engine coolant and transfer it to air passing through the heater core.
Thermostatic Expansion Valve (TXV)
The TXV (Thermostatic Expansion Valve) provides a restriction to the flow of refrigerant from the high-pressure side of the refrigerant system and separates the low-pressure and high-pressure sides of the refrigerant system. Refrigerant entering and exiting the evaporator core passes through the TXV (Thermostatic Expansion Valve) through 2 separate flow paths. An internal temperature sensing bulb senses the temperature of the refrigerant flowing out of the evaporator core and adjusts an internal pin-type valve to meter the refrigerant flow into the evaporator core. The internal pin-type valve decreases the amount of refrigerant entering the evaporator core at lower temperatures and increases the amount of refrigerant entering the evaporator core at higher temperatures.
Underbody Auxiliary Air Conditioning (AC) Lines
The 2 underbody auxiliary A/C (Air Conditioning) lines are part of a bundle of 4 aluminum tube assemblies of various sizes bracketed together and fastened to the underbody of the vehicle.
The underbody auxiliary A/C (Air Conditioning) lines have these features:
- The underbody auxiliary evaporator A/C (Air Conditioning) liquid line is an aluminum tube assembly that carries refrigerant from the front evaporator liquid inlet supply line to the auxiliary evaporator inlet.
- The underbody auxiliary evaporator A/C (Air Conditioning) suction line is a 15.875 mm (0.625 in) aluminum tube assembly that carries refrigerant from the auxiliary evaporator to the front evaporator outlet suction line.
Underbody Auxiliary Heater Lines
The 2 underbody auxiliary heater lines are part of a bundle of 4 aluminum tube assemblies of various sizes bracketed together and fastened to the underbody of the vehicle.
The underbody auxiliary heater lines have these features:
- The underbody auxiliary heater inlet line is an aluminum tube assembly that carries coolant from the engine coolant supply line to the auxiliary heater core inlet.
- The underbody auxiliary heater outlet line carries coolant from the auxiliary heater core to the front heater core outlet line.