Dual Zone Electronic A/C System-Operating Modes
The driver can select from eight different modes of operation from the
Heater-A/C control. The Heater-A/C control can initiate two additional purge
and delay modes when certain conditions exist.
Off
The following actions occur when the user selects the OFF mode:
| • | The blower motor turns on. |
| • | The A/C compressor turns off. |
| • | The vacuum electrical solenoid does not apply vacuum to any of
the vacuum actuators. |
| | When the vehicle is moving, the air that flows over the vehicle increases
the air pressure in front of the windshield. Some of the air is forced into
the outside air inlet. The air is forced through the blower case and out
of the outlets/vents. This is called ram air. Vacuum would allow ram air
to travel to all of the outlets/vents. |
| • | The temperature control valve circuitry is still activated. |
| | The heater-A/C control assembly completes the following functions: |
| • | Operates the air mix valves |
| • | Attempts to match the actual in-vehicle temperature to the set
temperature |
Because the compressor is turned off in the OFF mode, the system air
can be warmed, but not cooled.
Auto
The following actions occur when the user selects the AUTO mode:
| • | The control assembly turns on the AUTO and SET temperature indicators. |
| • | The blower indicator turns off. This indicates that auto control
is in effect. |
The driver can override the auto blower control by pressing the fan
speed button.
The heater-A/C control assembly evaluates the information that is supplied
by its network of sensors. The heater-A/C control assembly also determines
which of the following modes is required:
The control assembly then energizes the appropriate solenoid(s) to enter
the chosen mode.
The information that is supplied to the heater-A/C control assembly
also determines whether the system draws in outside air or recirculates the
inside air.
A/C
The following actions occur when the user selects the A/C mode:
| • | The heater-A/C control assembly illuminates the A/C LED. |
| • | The compressor is activated if the ambient temperature is above
3° C (38° F). The compressor runs in order to maintain
the evaporator core temperature at about 3° C (38° F). |
| • | The A/C compressor is automatically commanded in the following
modes if the ambient temperature is above 1.7-4.4°C (35-40°F): |
| • | The heater-A/C control programer completes the following actions: |
| - | Determines the correct air discharge |
| - | Powers the electric temperature valve actuators |
| - | The action enables the electric temperature valve actuators to move
the temperature valves to the proper position. |
Mode
The MODE button will operate
the following controls when they are selected on the control head assembly:
The control assembly will display which mode has been selected.
Defog
The following actions occur when the user selects the DEFOG mode:
| • | The blower motor turns on. |
| • | The user can manually adjust the blower speed by pressing the
fan speed button. |
| • | The A/C LED illuminates. |
| • | The compressor is activated if the ambient temperature is above
4.4° C (40° F). The compressor runs in order to maintain
the evaporator core temperature at about 3° C (38° F). |
| • | The heater/defroster door is in a mid position. This position
causes air to flow to the defroster outlets and the floor outlets. This is
the desired air flow for DEFOG mode. |
| • | Air flow occurs in the following manner: |
| • | The blower pulls outside air into the system. |
| • | The air is cooled and dehumidified. |
| • | The air is passed thru the heater core to heat. |
| • | The air flows out of the floor outlets and the defroster outlets. |
| • | The A/C control assembly determines the required air discharge and positions
the air mix valves correctly. |
Bi-Level
The following actions occur when the user selects the BI-LEVEL mode:
| • | The blower motor turns on. |
| • | The user can manually adjust the blower speed by pressing the
fan speed button. |
| • | The vacuum electrical solenoid vents the mode vacuum actuator. |
| • | Vacuum is applied to the heater-defroster actuator. |
| • | The valves are in the following positions: |
| - | The mode valve is in the bi-level position. |
| - | The heater-defroster valve is in the closed position. |
| - | The air inlet valve is in the outside air position. |
| • | The blower pulls outside air into the system. |
| | If the user selects A/C, the following actions occur: |
| - | The air is cooled and dehumidified. |
| - | The air is heated, as needed. |
| - | The air flows out of the instrument panel outlets and the floor
outlets. |
| - | The A/C control assembly determines the required air discharge and positions
the air mix valves correctly. |
Upper
The following actions occur when the user selects the UPPER mode:
| • | The blower motor turns on. |
| • | The user can manually adjust the blower speed by pressing the
fan speed button. |
| • | The vacuum electrical solenoid applies vacuum to the mode actuator. |
| • | The air inlet valve is in the outside air position. |
| • | The mode valve is in the upper (vent) position. |
| • | The blower pulls outside air into the system. |
| | If the user selects A/C, the following actions occur: |
| - | The air is cooled and dehumidified. |
| - | The air is heated, as needed. |
| - | The air flows out of the instrument panel outlets. |
Lower
The following actions occur when the user selects the LOWER mode:
| • | The blower motor turns on. |
| • | The user can manually adjust the blower speed by pressing the
fan speed button. |
| • | The vacuum electrical solenoid applies vacuum to the heater-defroster
actuator. |
| • | The valves are in the following positions: |
| - | The model valve closes. This position allows air to travel to
the heater-defroster valve. |
| - | The heater-defroster valve is in the heater mode position. |
| - | The air inlet valve is in the outside air position. |
Recirc
The inlet air to the module is drawn from the interior of the vehicle
when the user selects the RECIRC mode.
The RECIRC mode permits the maximum level of air cooling and dehumidification.
The user can select the RECIRC mode when any the following modes are
in use:
RECIRC is not available when the FRONT DEFROST mode is in use. The choice
of RECIRC in this case could cause windshield fogging.
The RECIRC function is usually cancelled when either of the following
actions occur:
| • | The user changes from automatic mode to manual mode. |
| • | The user changes from manual mode to automatic mode. |
The RECIRC function is not cancelled if the microprocessor requests
RECIRC due to the input that the sensor receives.
Front Defrost
The following actions occur when the user selects the FRONT DEFROST
mode:
| • | The blower motor turns on. |
| • | The user can manually adjust the blower speed by pressing the
fan speed button. |
| • | The A/C LED illuminates. |
| • | The compressor is activated if the ambient temperature is above
3° C (38° F). The compressor runs in order to maintain
the evaporator core temperature at about 3° C (38° F). |
| • | The vacuum electrical solenoid applies vacuum to the heater/defroster
actuator. |
| • | The valves are in the following positions: |
| - | The air inlet valve is in the outside air position. |
| - | The mode valve is closed. |
| • | The blower pulls outside air into the system. |
| | The following actions occur: |
| - | The air is cooled and dehumidified. |
| - | The air flows out of the defroster outlets. |
| - | The A/C control assembly determines the required air discharge temperatures
and positions the air mix valves correctly. |
Rear Defog
The following actions will occur if the user pushes the REAR DEFOG button:
| • | The LED in the switch will illuminate. |
| • | The first operation of the button will cause the REAR DEFOG to
operate for ten minutes. |
| | The second and consecutive operations of the button will cause the REAR
DEFOG to operate for 5 minutes. |
| • | Any activation while the rear defog LED is illuminated will cause
the rear defog operation to be turned off. |
