A/C Refrigerant System Operation

R-134A REFRIGERANT SYSTEM
Prompted by environmental concerns, Ford Motor Company is now producing vehicles equipped with non-chlorofluorocarbon (non-CFC) air conditioning systems. The new refrigerant used is R-134a, a hydrofluorocarbon that has no chlorine molecule, which destroys the atmosphere's ozone layer. R-134a systems function in the same manner as R-12 systems except for minimal operating pressure differences and component variations.
Escort and Tracer vehicles use the R-134a A/C system. This system uses different components, refrigerant, and refrigerant oil than the R-12 A/C systems used in previous years.
It is important to understand that R-134a and R-12 air conditioning systems are not entirely the same. They have components that are slightly different from one another and, in some cases, service requirements are also different. However, the most important thing to understand is that R-134a refrigerant, refrigerant oil, and components can only be used on R-134a systems while R-12 refrigerant, refrigerant oil, and components can only be used on R-12 systems. While these two types of A/C systems operate and function in a nearly identical manner, the refrigerant, refrigerant oil and components are not compatible.
R-134a systems require the use of dedicated special service tools and equipment. R-134a special service tools and equipment that come in contact with R-l34a refrigerant or refrigerant oil can only be used on R-134a A/C systems. R-12 special service tools and equipment cannot be used on R-134a A/C systems and vice versa.

MANUAL CLIMATE CONTROL SYSTEM
The control components consist of:





Item Description
1 Heater Blower Motor Switch
2 Temperature Control Switch
3 Function Selector Switch
4 Heated Back Window Switch
5 Heater Temperature Cable
6 Panel Airflow Door Vacuum Control Motor
7 Defrost/Floor Door Vacuum Control Motor
8 A/C Blower Motor Resistor
9 Air Inlet Door Vacuum Control Motor

The manual climate control system heats or cools the vehicle depending on the function selector position and the temperature selected. Function selector position determines heating or cooling and air distribution. The temperature control setting determines air temperature. The heated back window switch operates the heated back window.

Control System Inputs
The climate control system inputs are used to:
^ Select air inlet source (fresh/recirculated). Select blower motor speed.
^ Select discharge air temperature (temperature blend).
^ Select discharge air location (defrost, panel, floor).
^ Select A/C compressor clutch operation. Select heated back window operation.





Control System Outputs
Air Management Doors
The air management doors are operated by vacuum control motors and a heater temperature cable. The A/C air inlet door and distribution doors are controlled by vacuum control motors and the function selector switch. The air temperature control door is controlled by the heater temperature cable and the temperature control switch.

Blower Motor Circuit
The blower motor circuit consists of the heater blower motor switch, the A/C blower motor resistor and the A/C blower motor.
Blower motor speed is determined by changing the current flow to the A/C blower motor using resistors. The heater blower motor switch has four speeds that are obtained using three resistors that are wired in series. The A/C blower motor resistor is wired into the A/C blower motor ground circuit.
^ High Speed - Current through the A/C blower motor bypasses all resistors and travels directly to ground.
^ Medium High Speed - Current travels through one resistor and then to ground, slowing down current flow and the A/C blower motor.
^ Medium Low Speed - travels through two resistors and then to ground, slowing down current flow and the A/C blower motor.
^ Low Speed - Current travels through all three resistors, adding the highest resistance and causing the A/C blower motor to run at its slowest speed.
The thermal limiter is integral to the A/C blower motor resistor and serves as a temperature protection device. The thermal limiter is wired in series with the A/C blower motor resistor and opens when the resistor reaches approximately 121°C (250°F). When the thermal limiter opens, the A/C blower motor will only operate at high speed. The thermal limiter does not reset; once open, the A/C blower motor resistor must be replaced.

Compressor Clutch Circuit
An A/C clutch drives the A/C compressor shaft. When voltage is applied to the A/C clutch field coil, the clutch plate and hub assembly (which is connected to the A/C compressor shaft) is drawn by magnetic force toward the A/C clutch pulley, which rotates freely on the A/C compressor front head casting. The magnetic force locks the clutch plate and hub assembly and the A/C clutch pulley together as one unit. The A/C compressor shaft then turns with the A/C clutch pulley. When voltage is removed from the A/C clutch field coil, springs in the A/C clutch move the clutch plate away from the A/C clutch pulley and the A/C compressor shaft stops rotating.

Heated Back Window
The heated back window switch supplies power to the heated back window grid wires. The heated back window switch operates through the safety belt warning chime to limit the time of operation to fifteen minutes. If more time is necessary to clear the back window, the heated back window switch can be pressed again for another fifteen minutes of operation. The heated back window switch is mounted in the Integrated Control Panel (ICP) and cannot be repaired separately.

AIR DISTRIBUTION
The air distribution system routes air to the designated registers. This is accomplished when air enters the heater through the A/C air inlet duct and is routed to the desired outlets by the distribution doors. The air distribution system consists of:





Item Description
1. A/C Side Window Demister Register
2. A/C Register
3. A/C Side Window Demister and Hose
4. Windshield Defroster Hose Nozzle
5. A/C Outlet Duct
6. A/C Evaporator Register Duct
7. Windshield Defroster Nozzle Connector
8. A/C Air Inlet Duct
9. Heater
10. Rear Seat Airflow Duct
11. Instrument Panel Upper Finish Panel

Air Ducts and Registers
Air ducts route air to designated areas of the air distribution system. These areas are the floor ducts, rear seat airflow ducts, A/C registers, side window demisters and windshield defroster hose nozzles. The A/C registers are adjustable and are used to aim the discharged air to the desired area. The floor duct, side window demisters, and windshield defroster hose nozzles are non-adjustable.

A/C Air Inlet Door
There are two sources of air available to the air distribution system: recirculated air and fresh air.
a. Recirculated air is only used during MAX A/C and OFF modes.
b. Fresh air is used in all other modes.
The A/C air inlet door controls fresh and recirculated air.

Distribution Doors
The distribution door positions are determined by the control components. The distribution doors open and close air flow passages inside the heater to establish air flow direction. There are two distribution doors inside the heater: the panel/defrost door and the panel/floor door.
a. The panel/defrost door can be positioned either to block or to direct air to the panel ducts or defrost ducts.
b. The panel/floor door can block or direct air to the panel ducts or the floor ducts.

Air Temperature Control Door
Temperature control is achieved by the air temperature control door. The position of the air temperature control door determines how much air passes through the heater core, thus controlling the temperature of the air delivered to the passenger compartment.

System Air Flow
The volume of air moving through the climate control system is controlled by the blower motor switch. The path that the air takes as it moves into and through the climate control system is controlled by the function switch.




OFF




PANEL




PANEL/FLOOR




FLOOR




FLOOR/DEFROST




DEFROST




Max A/C