A/C Refrigerant System Operation

Refrigerant System:

REFRIGERANT SYSTEMS
The refrigerant used in this system is R-134a.
- 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 an R-134a system.
- Never mix R-12 and R-134a refrigerants or oils; they are not compatible.

A/C REFRIGERANT SYSTEM
The A/C refrigerant system is a clutch-cycling, orifice-tube type. The system components are as follows:
- A/C compressor
- A/C clutch
- A/C condenser core
- A/C evaporator core
- suction accumulator/drier
- necessary refrigerant lines

System operation is controlled by the following:
- A/C evaporator core orifice
- A/C cycling switch
- A/C pressure cut-off switch
The refrigerant system incorporates an A/C compressor controlled by an A/C cycling switch.

The A/C cycling switch:
- senses A/C evaporator core pressure to control A/C compressor operation.
- uses this method of compressor control to stop compressor operation during ambient temperatures below approximately 10°C (50°F) and to prevent A/C evaporator core from icing during normal system operation.

An A/C compressor relief valve is installed in the A/C manifold and tube to protect the refrigerant system against excessive refrigerant pressures.

Operation of the A/C clutch is dependent on signals from the Powertrain Control Module (PCM). The system is programmed to interrupt compressor operation when certain conditions exist. The A/C clutch can be shut off (or kept off) for several seconds:
- at engine start-up.
- at high engine speeds.
- during acceleration.
- when the engine coolant temperature exceeds a predetermined temperature.
- during low engine idle conditions (approximately 200 rpm below low idle specifications).





REFRIGERANT FLOW
During stabilized (A/C system shutdown) conditions, refrigerant system pressures are equalized on both the high and low sides of the refrigerant system.

When an A/C, mix or defrost function is selected and vehicle requires cooling, the system operates as follows:
- The A/C clutch field coil is energized and the A/C clutch is pulled into contact with the belt-driven A/C clutch pulley.
- The A/C clutch then rotates the compressor shaft.
- When the A/C compressor shaft is rotated, the refrigerant vapors from the suction side of the refrigerant system are compressed into a decreasingly smaller area, increasing the refrigerant vapor pressure and also raising the refrigerant vapor temperature.
- The high-pressure and high-temperature A/C compressor discharge refrigerant vapor is released into the A/C condenser core assembly through the A/C manifold and tube.
- In the A/C condenser core, high pressure refrigerant vapor condenses into a high pressure liquid when heat is removed from the refrigerant vapor by outside air passing over A/C condenser core fins and tubing.
- High pressure liquid refrigerant from the bottom of the A/C condenser core enters the inlet side of the A/C evaporator core orifice.
- Refrigerant pressure is reduced in the A/C evaporator core as a result of the flow restriction produced by the A/C evaporator core orifice and the A/C compressor suction.
- As passenger compartment or outside airflow passes over the plate/fin sections of the A/C evaporator core, the refrigerant inside absorbs the heat and changes into a vapor.
- A/C compressor suction draws the vaporized refrigerant and oil mixture into the suction accumulator/drier where the heavier oil-laden vapors fall to the bottom and the lighter vapors and oil mixture continue their path to the A/C compressor through the A/C manifold and tube.

REFRIGERANT LINE CONNECTIONS





Spring Lock Coupling
The spring lock coupling is a refrigerant line coupling held together by a garter spring inside a circular cage.
- When the coupling is connected together, the flared end of the female fitting slips behind the garter spring inside the cage of the male fitting.
- The garter spring and cage then prevent the flared end of the female fitting from pulling out of the cage.
- Two O-rings are used to seal between the two halves of the coupling.
- These O-ring seals are green in color and are made of special material.
- Use only the green O-ring seals listed in the Ford Master Parts Catalog for the spring lock coupling.
- A plastic indicator ring is used on the evaporator core spring lock couplings to indicate, during vehicle assembly, that the coupling is connected. Once the coupling is connected, the indicator ring is no longer necessary but will remain captive by the coupling near the cage opening.
- The indicator ring may also be used during service operations to indicate connection of the coupling.




A/C HEATER SYSTEM, MANUAL
The manual A/C-heater system has the following features:
- 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 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 vehicle to a comfortable level. Cooling or heating can then be adjusted to maintain desired temperature.
- The function selector knob can be turned on after the engine is warm. 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).

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 p0sitions except OFF, VENT and FLOOR.

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 vacuum control motor is used to store engine produced vacuum needed to operate the vacuum control motor.
- vacuum control motor is attached to the A/C evaporator housing.
- A/C vacuum check valve prevents accumulated vacuum from returning to the engine.




CLIMATE CONTROL ASSEMBLY
The climate control assembly has three control knobs:
- The air flow control or function selector knob is a vacuum selector valve combined with an internal electrical switch.
- The temperature control knob, which controls the position of the A/C temperature control door, is mounted on A/C evaporator case.
- The blower motor control knob is an electrical switch that 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-heater function selector switch, which is part of the heater control.
- The function selector knob has the following positions: OFF, VENT, FLOOR, MIX and DEFROST.
- The A/C-heater function selector switch combines a vacuum selector valve with an internal electrical switch.

Vacuum Control Diagram:

Vacuum Control Chart:

- The vacuum selector valve directs source vacuum to various vacuum control motors. Refer to the System Airflow Schematic and Vacuum Control Chart.
- An internal single-pole electrical switch is also controlled by the selector. The switch controls the electrical supply to the 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 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 case.
- Temperature is then regulated by mixing the portion of the air directed through the heater core 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 air that flows through and around the heater core, after which it is then mixed and directed into the distribution heater air plenum chamber.
- Air is finally directed to the heater outlet floor duct, windshield defroster hose nozzle or the instrument panel A/C registers, according to the function selector knob position.

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.

System Airflow Schematic:

SYSTEM AIRFLOW DESCRIPTION

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 recirc air is admitted to the system.
- the windshield defroster door is at no vacuum and the heater air damper door is at full vacuum, closing off the passages to the defrosters.
- 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 is off.

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 those previously described for 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 recirc air and admit outside air. From there, airflow is directed through the system to the instrument panel A/C registers.
- the heater air damper door is at no vacuum to block airflow to the heater outlet floor duct.
- the windshield defroster door is at full vacuum, closing off airflow to the windshield defroster hose nozzle.
- 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 to block recirc air and admit outside air.
- the heater air damper door is in the vacuum position closing off airflow to the windshield defroster hose nozzle.
- 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 to block air circulation to the panel A/C register.
- 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 duct and windshield defroster hose nozzle.
- 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 to admit outside air.
- both the heater air damper door and the windshield defroster doors 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 hose.
- the temperature control knob setting will determine the amount of heat being blended into the airflow.
- The blower motor is on.