A/C Refrigerant System Operation
R-134a Refrigerant SystemNOTE: Do not use R-12 service tools and equipment when servicing an R-134a system.
Never mix R-12 and R-134a refrigerants or oils. They are not compatible.
- The system uses a Non-Chlorofluorocarbon (non-CFC) based refrigerant R-134a.
- R-134a is a Hydrofluorocarbon (HFC) based refrigerant.
- R-134a requires use of PAG Compressor Oil Motorcraft YN-12c F7AZ-19589-DA or equivalent meeting Ford specification WSH-M1C231-B.
A/C-Heater System, Manual
- The system has a split-case design, integral A/C blower.
- The system controls the temperature and, during A/C operation, reduces the relative humidity of air inside the vehicle.
- Control knobs are provided to adjust the desired temperature and control system functions.
- The system delivers heated or cooled air to the vehicle interior.
- A/C blower motor speeds can be adjusted for desired airflow.
- Outside air is drawn from the cowl air inlet just below the windshield during all system operations except for MAX A/C cooling (when recirculated air is used).
Heating/Defrosting/Ventilation System
In the manual A/C-heater system:
- Heat can be added to system airflow in any of the function selector knob positions except OFF.
- Air direction through the system is determined by the A/C-heater function selector switch position.
- Quantity of air flowing through the system is determined by the position of the heater blower motor switch.
Ventilation System
In the manual A/C-heater system:
- Outside air is drawn from the cowl in all function selector knob positions except OFF and MAX A/C.
- Cooling and dehumidification of ventilation air occurs in all function selector knob positions except OFF, PANEL, PANEL/FLOOR and FLOOR.
Climate Control Assembly
These vehicles group together the following systems into a single integrated control panel:
- AM/FM stereo radio
- clock
- rear window defroster switch
- climate control
- optional full-logic cassette
The climate control assembly has three control knobs:
- The blower motor control knob, attached to the A/C electronic blend door actuator, provides four speeds of blower motor operation.
- The air flow control or function selector knob, attached to the A/C-heater function selector switch, controls vacuum and electrical applications.
- The temperature control knob, attached to the potentiometer, controls the position of the A/C electronic blend door actuator mounted on the A/C evaporator housing.
Air Flow Control
Air flow control is accomplished in the following manner:
- Primary control is through the function selector knob mounted on the A/C-heater function selector switch, which is part of the integrated control panel.
- The function selector knob has the following positions:
- OFF
- MAX A/C
- A/C
- PANEL
- PANEL/FLOOR
- FLOOR
- FLOOR/DEFROST
- DEFROST.
- The A/C-heater function selector switch combines a vacuum selector valve with an internal electrical switch.
Vacuum Control Diagram
Vacuum Control Chart
System Airflow Schematics
Item Description
1 Pollen Filter (Optional)
2 Heater and A/C Air Inlet Duct Door
3 Supplemental A/C Air Inlet Duct Door
4 Blower Motor
5 A/C Evaporator Core
6 Heater Core
7 Secondary A/C Air Temperature Control Door
8 Heater Air Damper Door
9 Supplemental A/C Damper Door (Rear Seat A/C Registers Only)
10 Windshield Defroster Door
11 Supplemental A/C Air Temperature Control Door
12 Primary Air Temperature Control Door
- The vacuum selector valve directs source vacuum to various vacuum control motors. Refer to the Vacuum Control Diagram, System Airflow Schematics and Vacuum Control Chart.
- Two internal, single-pole electrical switches are also controlled by the A/C-heater function selector switch. The combination of these electrical switches controls the electrical supply to the A/C clutch and heater blower motor switch.
- The position of the function selector knob determines the manner in which the system will operate.
- Each position of the function selector knob is detented for positive engagement.
Temperature Control
The temperature control operates in the following manner:
- Temperature control of the manual A/C-heater system is determined by the position of the temperature control knob (between COOL and WARM).
- This control knob is connected to a potentiometer mounted in the integrated control panel. This potentiometer is electrically connected to the A/C electronic blend door actuator that operates the A/C air temperature control door.
- The A/C electronic blend door actuator contains a reversible electric motor, another potentiometer and a printed circuit board. The wiper of the potentiometer is connected to the actuator output shaft and moves with the output shaft to indicate the position of the A/C air temperature control door.
- Battery voltage is applied to the ends of each potentiometer. The voltage available at each wiper indicates the position of the potentiometer. The printed circuit board drives the actuator in whichever direction is necessary to make the actuator wiper voltage agree with the control wiper voltage.
System uses a reheat method to provide conditioned air to passenger compartment.
- All airflow from the blower motor passes through the A/C evaporator housing where it can be cooled and dehumidified.
- Temperature is then regulated by reheating a portion of the cooled dry air and blending it with the remaining cool air to the desired temperature.
- Temperature blending is varied by the A/C air temperature control door which regulates the amount of cooled air that flows through and around the heater core where it is mixed and distributed.
Blower Motor Control
Blower motor operation is controlled by the heater blower motor switch.
- The heater blower motor switch provides four manually-selected blower speeds and may be operated in any position to select the desired amount of airflow.
- The heater blower motor switch and the heater blower motor switch resistor are positioned in the ground circuit of the blower motor.
Vacuum Hoses
A vacuum hose harness, which is attached to the back of the A/C-heater function selector switch, directs vacuum to three doors in the manual system:
- a heater air damper door
- a windshield defroster door
- a heater and A/C air inlet duct door
The A/C vacuum reservoir tank and bracket is used to store engine produced vacuum needed to operate the vacuum control motor.
- It is located under the RH front fender.
- An A/C vacuum check valve prevents accumulated vacuum from returning to the engine.