Manual Climate Control
MANUAL CLIMATE CONTROL
The manual climate control components are used to select:
- air inlet source (outside or recirculated).
- blower motor speed.
- discharge air temperature (temperature blend).
- discharge air location (defrost, panel, floor).
- A/C compressor operation.
Control System Inputs - Manual Climate Control
Function Selector Switch
The function selector switch combines a vacuum selector valve that determines air distribution and an electrical switch to supply battery voltage to the A/C compressor circuit and the blower motor circuit. When the function selector switch is in the MAX A/C, DEFROST or FLOOR/DEFROST positions, the A/C compressor will be operational regardless of the A/C request switch status.
Climate Control Assembly
The climate control assembly integrates the temperature control switch, A/C request button and rear defog switch into a single unit.
The temperature control switch setting determines air temperature. Temperature selection is accomplished with a potentiometer (temperature control switch) connected to the temperature blend door actuator. Movement of the temperature control switch from COOL (blue) to WARM (red) causes a corresponding movement of the temperature blend door and determines the air discharge temperature that the air distribution system will maintain. The temperature control switch is an integral part of the manual climate control assembly and cannot be installed separately.
The A/C request switch determines A/C compressor operation, except when the function selector switch is in the OFF, MAX A/C, DEFROST or FLOOR/DEFROST positions. The A/C request switch is an integral part of the manual climate control assembly and cannot be installed separately.
The rear defog button signals activation of the heated backlight and heated mirrors. The rear defog button is an integral part of the manual climate control assembly and cannot be installed separately.
Blower Motor Switch
The blower motor switch controls blower motor speed by supplying voltage to the blower resistor circuits.
Control System Outputs - Manual Climate Control
Blower Motor Resistor
The blower motor resistor:
- is located on the plenum chamber near the blower motor.
- has three resistor elements mounted on the resistor board to provide four blower motor speeds.
- has an overheating device (thermal limiter) that will open the resistor coil when the temperature reaches approximately 184°C (363°F), interrupting the blower motor operation in all speeds except high.
- is serviced as an assembly. The thermal limiter cannot be reset and is not serviceable.
Depending on the blower motor switch position, series resistance is added or bypassed in the blower motor circuit to decrease or increase blower motor speed.
Temperature Blend Door Actuator
The temperature blend door actuator:
- is located on the plenum chamber.
- moves the temperature blend door on command of the temperature control switch.
- contains a reversible electric motor.
Vacuum Control Motors
The three vacuum control motors have the following characteristics:
- They are actuated by the function selector switch.
- They position the plenum doors to direct system airflow to the vehicle interior as determined by the function selector switch settings.
- The air inlet door vacuum control motor is a single-diaphragm actuator with a single vacuum source.
- The airflow mode door vacuum control motors are double-diaphragm actuators with two separate vacuum sources to allow the actuator to fully retract or partially retract.
- When vacuum is applied to both vacuum sources, the actuator will fully retract.
- When vacuum is applied only to the partial stage vacuum source, the actuator will partially retract.
Coolant Control Valve
The coolant control valve is actuated by the air inlet vacuum circuit. When the air inlet vacuum circuit is closed (at full vacuum), coolant flow through the heater core is shut off and A/C cooling efficiency is increased.