A/C System - Manual

DESCRIPTION
The A/C refrigerant system is the fixed orifice tube-cycling clutch type. The system components are the compressor, magnetic clutch, condenser, evaporator, suction accumulator/drier, and the necessary connecting refrigerant lines. System operation is controlled by the fixed orifice tube and the clutch cycling pressure switch.

R-12 A/C Refrigerant System:

REFRIGERANT SYSTEMS
Taurus/Sable vehicles offer two types of A/C systems. The main difference between these systems involve the mandatory requirement of the use of different refrigerants. The two types of A/C systems are:
1. Fixed orifice tube type system with cycling clutch using the chlorofluorocarbon (CFC) based Refrigerant-12 (R-12).
2. Fixed orifice tube type system with cycling clutch using the Non-Chlorofluorocarbon (Non-CFC) based Refrigerant-134a (R-134a).

NOTE: When diagnosing or servicing the A/C refrigerant system, time can be saved if the proper procedures are carefully followed.

NOTE: The following conditions may cause the A/C compressor to momentarily disengage:
1. Wide-open throttle (WOT).
2. Very high, or too low engine speed.
3. Engine cranking.
4. High engine coolant temperature.
5. A low or no refrigerant condition will also prevent the A/C compressor from engaging.

A/C-HEATER SYSTEM

A/C-Heater System Airflow:

The manual A/C-heater system is a vibration welded, split-case design integral blower system that controls the temperature and reduces the relative humidity of the air inside the vehicle. Control knobs are provided to adjust the desired temperature and system functions. The system will deliver heated or cooled air to maintain the vehicle interior temperature and comfort level. The blower speeds can be adjusted for more or less airflow as desired.

A/C-Heater Control Assembly:

Manual control of the passenger compartment temperature may be maintained in all function control settings, except when the system is turned off. In hot weather, it will cool the vehicle to a comfortable level. Cooling or heating can then be adjusted as required to maintain the desired temperature.

For cold weather conditions, the system may be turned off by placing the function selector knob in the OFF position. This will minimize the discharge of cold air and delay the operation of the system while the engine coolant warms. After the engine is warm, the function selector knob can be turned ON, and the system will heat the vehicle to the desired temperature.

Outside air is drawn from the cowl air inlet just below the windshield during all system operations except MAX-A/C cooling, when recirculated air is used.

CONTROL OPERATION
The manual A/C-heater control includes a function selector knob which has the following positions: OFF, MAX-A/C, NORM-A/C, VENT, FLOOR, MIX, and DEFROST. The position of the knob determines the manner in which the system will operate. The temperature control knob manually sets the desired comfort temperature, and the fan control knob controls the volume of air movement. Each position of the function selector knob and fan control knob is detented for positive engagement. The fan control knob provides four manually selected blower speeds, and may be operated in any position of the function selector knob to select the desired amount of airflow.

TEMPERATURE CONTROL
Temperature control of the manual A/C-heater system is determined by the position of the temperature control knob on the control assembly and is accomplished by means of a control cable between the control assembly and the temperature blend door. System airflow is manually controlled by the control assembly. A vacuum selector valve, controlled by the function selector knob, distributes vacuum to the various door vacuum motors, which in turn direct the airflow through the system.

The system uses what is called a "reheat" method to provide conditioned air to the vehicle interior. With this method, all airflow from the blower passes through the evaporator core, where it is 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 temperature blend door, which controls the amount of cooled air that flows through or around the heater core, where it is mixed and directed into the distribution plenum. The air is finally directed to the heater ducts, the defroster nozzles, or the instrument panel registers according to function selector knob position.

SYSTEM AIRFLOW
The actions that take place when the function select knob is rotated to each of its seven detent locations are as follows:

Airflow Chart 1 (OFF, MAX A/C, NORM A/C):

^ OFF, MAX A/C, NORM A/C

Airflow Chart 2 (VENT, FLOOR, MIX, And DEFROST):

^ VENT, FLOOR, MIX, and DEFROST

A/C System Schematic And Vacuum Control Chart:

^ The A/C System Schematic And Vacuum Control Chart shows the control assembly with its function selector knob in the OFF position, and its temperature control knob midway between its maximum WARM and maximum COOL settings. The fan knob is set at a low blower speed. Other blower speed settings include: MEDIUM LOW, MEDIUM HIGH and HIGH. The A/C System Schematic And Vacuum Control Chart also provides a schematic of the manual A/C-heater system and the doors which respond to full vacuum, partial vacuum, and no vacuum when supplied by a separate vacuum motor for each door. These doors are: air outside/recirculate door, a panel-defrost door in the plenum chamber, and a floor-panel door which is designed to provide full, partial, or no vacuum positions. The blend door is manually controlled by a cable and moves according to the position of the temperature control knob.
^ The blend door may be positioned anywhere within the range of its cable travel, from full heat to full cold.
^ The blower motor is OFF.

MAX A/C (RECIRCULATED AIR)
When the function selector knob is in the MAX A/C position:
^ The outside/recirculate door is at full vacuum, closing off outside air.
^ The floor-panel door is at no vacuum, blocking airflow to the floor registers.
^ The panel-defrost door is at full vacuum, closing off airflow to the defrosters.
^ Temperature control is usually set for maximum cold, but may be heated if desired.
^ Air will be picked up at the recirculating opening by the blower motor. Airflow across the evaporator core will be diverted past the heater core and then directed into the passenger compartment through the instrument panel registers.

The A/C System Schematic And Vacuum Control Chart shows the Function Selector Valve Detent Position chart and a schematic of mode selector knob functions.

Airflow Chart 1 (OFF, MAX A/C, NORM) and Airflow Chart 2 (VENT, FLOOR, MIX, And DEFROST) correlate specific airflow conditions which occur when a given function selector knob setting is made.

OFF
When the function selector knob is in the OFF position:
^ The outside/recirculate door is at full vacuum. As a result, outside air is closed off and recirculate air is admitted to the system.
^ The panel-defrost door and the floor-panel door are both at full vacuum, closing off the passages to the defrosters.

NORM A/C (OUTSIDE AIR)
When the function selector knob is in the NORM A/C position:
^ The outside/recirculate door is set at no vacuum. This blocks the recirculate passage and allows the admittance of outside air.
^ All other door positions are the same as those previously described for the MAX A/C setting.
^ The temperature setting can be changed manually as desired.
^ The compressor will be operating when NORM A/C is selected.

VENT
When the function selector knob is in the VENT position:
^ The outside/recirculate 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 registers.
^ The floor-panel door is at no vacuum to block airflow to the floor registers.
^ The panel-defrost door is at full vacuum, closing off airflow to the defrosters.
^ The air conditioned airflow is admitted into the system when the function selector knob is in the VENT position, but the temperature control knob may be adjusted to heat the air, if desired.

FLOOR
When the function selector knob is in the FLOOR position:
^ The outside/recirculate door is in the no vacuum position, blocking recirculated air and admitting outside air.
^ The floor-panel door is in the vacuum position, closing off all but a minimum of airflow to the defrosters.
^ The blend door is positioned to mix air flowing through the heater core and air from outside to achieve the desired temperature level.
^ The panel-defrost door is in the no vacuum position, blocking air circulation to the panel registers.

MIX
When the function selector knob is in the MIX position:
^ The outside/recirculate air door and the panel-defrost door are in the no vacuum position.
^ The floor-panel door is in the partial vacuum position, allowing airflow to both panel registers and floor duct.
^ 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 outside/recirculate door is in the no vacuum position, admitting outside air.
^ Both the floor-panel and the panel-defrost doors are in the no vacuum position, so that the most of the incoming air is directed to the defroster nozzles. There is a slight air bleed to the floor registers.
^ The temperature control knob setting will determine the amount of heat introduced into the airflow.
^ The A/C clutch will also operate when the DEFROST position is selected. This dehumidifies incoming air and reduces windshield fogging.