Refrigerant System

R-134A REFRIGERANT SYSTEM

NOTE: 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 Motorcraft YN-12b refrigerant oil 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 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 SYSTEM
In the manual A/C-heater system:
^ Heat can be added to system air flow 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, VENT and FLOOR.







CLIMATE CONTROL ASSEMBLY
The climate control assembly has three control knobs:
^ The blower motor control knob, attached to the heater blower motor switch, provides four speeds of blower motor operation.
^ The temperature control knob controls the position of the A/C temperature control door mounted on A/C evaporator housing.
^ The function selector knob controls vacuum and electrical applications.

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 A/C control.
^ The function selector has the following positions:
- OFF, MAX A/C, NORM A/C, VENT, FLOOR, MIX and DEFROST
^ The A/C-heater function selector 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 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 is accomplished by means of an A/C temperature cable that operates the A/C air temperature control door.
^ Movement of the control knob from COOL to WARM 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 the 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 heating 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.
^ Is attached to the A/C evaporator housing.
^ 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.

OFF
When the function selector knob is in the OFF position:
^ The heater and A/C air inlet duct 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 no vacuum and the heater air damper is at full vacuum, closing off the passages to the windshield defroster hose nozzles.
^ The A/C air temperature control door position may be anywhere within the range of its cable travel from FULL HEAT to FULL COOL.
^ 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 heater and A/C air inlet duct 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.
^ Temperature control is usually set for maximum cold but may be heated if desired.
^ Air will be picked up at the recirculation opening by the blower motor. 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.

NORM A/C
When the function selector knob is in the NORM A/C position:
^ The heater and A/C air inlet duct door is set at no vacuum, blocking the recirculation passage and admitting outside air.
^ All other door positions are the same as the MAX A/C setting.
^ Temperature setting can be changed manually as desired.
^ The A/C compressor will be operating when NORM A/C is selected.
^ The blower motor is on.

VENT
When the function selector knob is in the VENT position:
^ The heater and A/C air inlet duct 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 no vacuum to block airflow to the floor heater outlet floor ducts.
^ The windshield defroster door is at full vacuum, closing off airflow to the windshield defroster hose nozzles.
^ The temperature setting can be changed manually as desired.
^ the blower motor is ON.

FLOOR
When the function selector knob is in the FLOOR position:
^ The heater and A/C air inlet duct door is in the no vacuum position, blocking recirculating air and admitting outside air.
^ The heater air damper door is in the vacuum position, closing off airflow to the windshield defroster hose nozzles.
^ The A/C air temperature control door can be positioned to mix air flowing through the heater core and air from outside to achieve the desired temperature level.
^ The windshield defroster door is in the no vacuum position, blocking air circulation to the panel A/C registers.
^ The blower motor is ON.

MIX
When the function selector knob is in the MIX position:
^ The heater and A/C air inlet duct door and the windshield defroster door are in the no vacuum position.
^ The heater air damper door is in the partial vacuum position, allowing airflow to both heater outlet floor ducts and windshield defroster hose nozzles.
^ The A/C compressor operates to dehumidify the air and reduce windshield fogging.
^ The blower motor is ON.

DEFROST
When the function selector knob is in the DEFROST position:
^ The heater and A/C air inlet duct door is in the no vacuum position, admitting outside air.
^ both the heater air damper door and the windshield defroster door are in the no vacuum position so that most of the incoming air is directed to the windshield defroster hose nozzles. There is also airflow to the A/C side window demister and hoses.
^ The temperature control knob setting will determine the amount of air directed through heater core.
^ The A/C compressor operates to dehumidify the air and reduce windshield fogging.
^ The blower motor is ON.