System Operation

R-134A REFRIGERANT SYSTEM
This application uses the R-134a A/C system.
- The R-134a system uses a non-chlorofluorocarbon (non-CFC) based refrigerant R-134a.
- R-134a is a hydrofluorocarbon (HFC) based refrigerant.
- R-134a requires use of Motorcraft YN-12b refrigerant oil or equivalent meeting Ford specification WSH-M1C231-B.
- Do not use R-12 service tools and equipment when servicing a R-134a system.
- Never mix R-12 and R-134a refrigerants or oils; they are not compatible.







A/C-HEATER SYSTEM, MANUAL
The manual A/C-heater system has the following features:
- Vibration welded single-case design, with integral A/C blower.
- Controls the temperature and, during A/C operation, reduces the relative humidity of air Inside the vehicle.
- Control knobs adjust the desired temperature and control system functions.
- The system delivers heated or cooled air to maintain the vehicle interior temperature and comfort level.
- A/C blower motor speeds can be adjusted for desired airflow.
- Manual temperature control can be maintained in all control settings except when system is turned OFF.
- In hot weather, the system will cool the passenger compartment air to a comfortable level.
- Cooling or heating can then be adjusted to maintain desired temperature.
- The function selector knob can be turned on at any time. The system will heat vehicle to desired temperature.
- 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 SYSTEM
In the manual A/C heater system:
- heat can be added to system airflow in any of the function selection knob positions except OFF.
- air direction through the system is determined by the A/C damper door 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 selection knob positions except OFF and MAX A/C.
- cooling and dehumidification of outside air occurs in all function selector knob positions except OFF, PANEL, PANEL/FLOOR and FLOOR.







CLIMATE CONTROL ASSEMBLY
The first three knobs on the A/C control control system functions. The fourth knob is for auxiliary A/C and heating control (if equipped).
- The air flow control or function selector knob controls vacuum and electrical applications.
- The temperature control knob controls the position of the A/C electronic door actuator motor and is mounted on A/C evaporator housing.
- The blower motor control knob, attached to the heater blower motor switch, provides four speeds of blower motor operation.

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 damper door switch which is part of the A/C control.
- The function selector knob has the following positions: OFF, MAX A/C, A/C, PANEL, PANEL & FLOOR, FLOOR, FLOOR & DEFROST and DEFROST.
- The A/C damper door switch combines a vacuum selector valve with an internal electrical switch.
- The vacuum selector valve directs source vacuum to various vacuum control motors. Refer to the Vacuum Control Diagram, System Airflow Schematic and Vacuum Control Chart.
- Two internal, single pole electrical switches are also controlled by the A/C damper door 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-BLUE and WARM-RED).
- This control is accomplished by means of an A/C electronic door actuator motor that operates the A/C air temperature control door.
- Movement of the control knob from COOL-BLUE to WARM-RED causes a corresponding movement on the A/C air temperature control door and determines the temperature that the system will maintain.

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/or around the heater core, where it is then 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 damper door switch controls these doors in the manual system:
- heater air damper door
- windshield defroster door
- 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 motors
- It is located on the RH wheel housing.
- An A/C vacuum check valve prevents accumulated vacuum from returning to the engine.

SYSTEM AIRFLOW DESCRIPTION
The illustrations contain system vacuum schematics and vacuum motor charts which show vacuum routings and airflow when the controls are set at their various positions.






- Vacuum Control Diagram






- Vacuum Control Chart






- System Airflow Schematic (Part 1 of 2)






- System Airflow Schematic (Part 2 of 2)

OFF
When the function selector knob is in the OFF position:
- the A/C damper inlet door is at full vacuum. As a result, outside air is closed off and recirculated air is admitted to the system.
- the windshield defroster door is at full vacuum and the heater air damper door is at no vacuum, closing off the airflow to the windshield defroster hose nozzle.
- the blower motor and A/C compressor are off.

MAX A/C
When the function selector knob is in the MAX A/C position:
- the A/C damper inlet door is at full vacuum, closing off outside air and admitting only recirculated air.
- the heater air damper door is at no vacuum, blocking airflow to the heater outlet floor duct.
- the windshield defroster door is at full vacuum, closing off airflow to the windshield defroster hose nozzles and directing airflow to the A/C registers.
- temperature control is usually set for full cool, but may be heated if desired.
- air will be picked up at the recirculation opening by the blower motor. With the temperature control set for maximum cold, airflow across the A/C evaporator core will be diverted past the heater core and then directed into the passenger compartment through the instrument panel A/C registers.
- the A/C compressor will be operating when MAX A/C is selected.
- the blower motor is on.

A/C
When the function selector knob is in the A/C position:
- the A/C damper inlet door is set at no vacuum, blocking the recirculation passage and admitting outside air.
- all other door positions are the same as outlined under MAX A/C.
- temperature setting can be changed manually.
- the A/C compressor will be operating when A/C is selected.
- the blower motor is on.

PANEL
When the function selector knob is in the PANEL position:
- the A/C damper inlet door, with no vacuum being applied, will block recirculated air and admit outside air. From there, air flows through the system to the instrument panel A/C registers,
- the heater air damper door is at full vacuum, airflow is directed to the instrument panel A/C registers,
- the windshield defroster door is at full vacuum, closing off airflow to the windshield defroster hose nozzles,
- the temperature setting can be changed manually to heat the air but air can not be cooled below outside temperature.
- the blower motor is on.

PANEL & FLOOR
When the function selector knob is in the PANEL & FLOOR position:
- the A/C damper inlet door is set at no vacuum blocking the recirculated passage and admitting outside air.
- the heater air damper door is in the partial vacuum position, allowing airflow to both heater outlet floor duct.
- the windshield defroster door is at full vacuum, closing off airflow to the windshield defroster hose nozzles,
- the temperature setting can be changed manually to heat the air but air can not be cooled below outside temperature.
- the blower motor is on.

FLOOR
When the function selector knob is in the FLOOR position:
- the A/C damper inlet door is in the no vacuum position, blocking recirc air and admitting outside air,
- the heater air damper door is in the no vacuum position, closing off airflow to the panel A/C registers.
- the air temperature control door may be positioned to mix air flowing through and around the windshield defroster door to achieve the desired temperature level.
- the windshield defroster door is in the vacuum position, closing off all but a minimum of airflow to the windshield defroster hose nozzle,
- the blower motor is on.

DEFROST & FLOOR
When the function selector knob is in the DEFROST & FLOOR position:
- the A/C damper inlet door is in the no vacuum position,
- the heater air damper door is in the full vacuum position, allowing no airflow to instrument panel A/C registers,
- the windshield defroster door is in the partial vacuum position, allowing airflow to both heater outlet floor duct and windshield defroster hose nozzles.
- the A/C compressor operates to dehumidify the air and reduce windshield fogging.

DEFROST
When the function selector knob is in the DEFROST position:
- the A/C damper inlet door is in the no vacuum position, admitting outside air,
- the heater air damper door is in the vacuum position blocking airflow to the instrument panel A/C registers,
- the windshield defroster door is in the no vacuum position, so that most of the incoming air is directed to the windshield defroster hose nozzles.
- the temperature control knob setting will determine the amount of air that is directed through the windshield defroster door and the amount that bypasses the windshield defroster door.
- the A/C compressor operates to dehumidify the air and reduce windshield fogging.
- the blower motor is on.