Climate Control General Information
CLIMATE CONTROL SYSTEMManual Climate Control System
The manual climate control system heats or cools the vehicle interior depending on the position of the function selector switch and the temperature selected. The position of the function selector switch determines heating or cooling and air distribution. The temperature control setting determines air temperature.
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, M2 (medium-low) and M1 (medium-high).
- gives the blower motor a direct path to ground through the blower motor switch, which allows the blower motor to operate in HI.
The temperature control switch actuates a cable attached directly to the temperature blend door located in the heater core housing.
The function selector switch:
- determines where the system airflow is directed.
- enables blower motor operation.
- combines a vacuum with 2 electrical switches.
- supplies power to the A/C clutch circuit in the MAX A/C, A/C, FLOOR/DEFROST and DEFROST positions.
Air Distribution
There are 2 sources of air available to the air distribution system:
- Outside air
- Recirculated air
Recirculated air is only used when the manual climate control mode selector is set in the MAX A/C or OFF modes.
Air distribution within the vehicle is determined by the function selector switch position. Air flow control doors are used to direct air flow within the A/C evaporator housing and heater. Vacuum control motors are used to position these air flow control doors.
The air distribution system is designed to provide air flow from the defrost nozzle when no vacuum is applied to any of the vacuum control motors. This is done to prevent a situation where defrost cannot be obtained due to a system vacuum leak.
Air enters the passenger compartment from the:
- instrument panel register.
- heater outlet floor duct.
- windshield defroster hose nozzle.
- side window demisters.
- rear footwell duct.
Passenger compartment air is exhausted from the vehicle through open windows or through the air extractors located in the rear of the vehicle.
Refrigerant System Dye
Fluorescent refrigerant system dye is added to the refrigerant system at the factory to assist in refrigerant system leak diagnosis using an approved ultraviolet blacklight. It is not necessary to add additional dye to the refrigerant system before diagnosing leaks, even if a significant amount of refrigerant has been removed from the system. New suction accumulators are shipped with a fluorescent dye wafer included in the desiccant bag which dissolves after approximately 30 minutes of continued A/C operation. It is not necessary to add dye after flushing or filtering the refrigerant system because a new suction accumulator is installed as part of the flushing or filtering procedure. Additional refrigerant system dye should only be added if more than 50% of the refrigerant system lubricant capacity has been lost due to a fitting separation, hose rupture or other damage.
Control Components
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
The climate control assembly has 3 system control inputs.
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, A/C, FLOOR/DEFROST or DEFROST positions, the A/C compressor will be operational. The function selector switch can be replaced separately from the climate control head unit.
Temperature Control Switch
The temperature control switch setting determines air temperature. Temperature selection is accomplished through a cable connected to the temperature blend door. 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 can be replaced separately from the climate control head unit.
Blower Motor Switch
The blower motor switch controls blower motor speed by adding or bypassing resistors in the blower motor switch resistor in all function selector switch positions except OFF. The blower motor switch can be replaced separately from the climate control head unit.
Control System Outputs
Blower Motor Resistor
The blower motor resistor:
- is located on the evaporator core housing behind the glove compartment.
- has 3 resistor elements mounted on the resistor board to provide 4 blower motor speeds.
- depending on the blower motor switch position, series resistance is added or bypassed in the blower motor circuit to decrease or increase the blower motor speed.
- 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 replaced as an assembly. The thermal limiter cannot be reset and cannot be repaired.
Temperature Blend Door Actuator
The temperature blend door actuator:
- is connected between the temperature control switch and the temperature blend door.
- moves the temperature blend door on the command of the temperature control switch.
Vacuum Control Motors
The vacuum control motors:
- direct system airflow to the vehicle interior as determined by the function selector switch.