HVAC System - Automatic: Other Ford Taurus IV

REMOTE CLIMATE CONTROL MODULE

The Remote Climate Control (RCC) module uses a microcomputer to analyze inputs from the in-car temperature sensor, ambient air temperature sensor, sunload sensor and function inputs made at the ICP by vehicle occupants. (Scheme 21)

Using these inputs, the RCC module determines the correct outputs for A/C compressor clutch engagement and blower speed. The RCC module also determines outputs controlling the A/C air temperature control door, heater air damper door, windshield defrost door, and the A/C air inlet door positions.

The A/C air temperature control door is operated by an electric door actuator motor. The remaining distribution doors are controlled by vacuum actuated motors.

Scheme 21

A/C PRESSURE CUT-OFF (DUAL PRESSURE) SWITCH

A/C pressure cut-off switch is located in manifold and tube assembly, between compressor and condenser. Switch interrupts compressor operation when discharge pressures rise above preset pressure. When pressure drops to a preset pressure, switch contacts close, allowing compressor operation. A second set of switch contacts are used for high speed fan operation. When discharge pressure reaches a preset pressure, switch contacts close, engaging high speed fan. When pressure drops to a preset pressure, switch contacts open, disengaging high speed fan. See A/C PRESSURE CUT-OFF SWITCH SPECIFICATIONS table.

A/C PRESSURE CUT-OFF SWITCH SPECIFICATIONS

A/C PRESSURE RELIEF VALVE

On 2000 models, pressure relief valve relieves high-side pressure build-up above 450 psi (31.6 kg/cm 2 ). On 2001 models, pressure relief valve relieves high-pressure build-up at 550-600 psi (38.7-42.2 kg/cm 2 ). Pressure relief valve prevents total loss of refrigerant and damage to A/C compressor and other system components. Pressure relief valve is incorporated into compressor manifold and tube.

A/C PRESSURE TRANSDUCER

A/C pressure transducer is mounted on a Schrader valve on A/C manifold and tube. A/C pressure transducer provides a voltage signal that is proportional to compressor discharge pressure. This allows pressure to be monitored by PCM.

FUNCTION & OVERRIDE BUTTONS

Note. Pressing MAX A/C and front defrost buttons simultaneously (until display changes) will switch between Fahrenheit and Celsius.

OFF Button

The OFF button will turn the EATC system off. The Vacuum Fluorescent Display (VFD) will be blank, unless the OUTSIDE TEMP function has been selected.

AUTO Button

Pressing the AUTO button will turn the EATC system on for fully automatic operation. The VFD will display AUTO and the selected temperature. The RCC module will maintain selected temperature by controlling compressor clutch operation, airflow direction, temperature blend door operation and blower speed.

TEMP Rocker Switch

Pressing the TEMP rocker switch once to the right will raise the selected temperature incrementally. If the rocker switch is pressed and held down, the selected temperature will be raised in one degree increments until switch is released or 85°F (29°C) is selected. If switch remains depressed after 85°F (29°C) is reached, the system will increase in a single step to maximum setting of 90°F (32°C). Pressing the rocker switch to the left will lower the temperature in a similar manner. Minimum selected temperature is 65°F (18°C).

OUTSIDE TEMP Button

Pressing OUTSIDE TEMP button will display ambient temperature on VFD. Temperature will remain displayed until OUTSIDE TEMP button or any other button is pressed.

FAN Rocker Switch

Pressing the FAN rocker switch to the right (+) will raise blower motor to desired speed. Pressing the rocker switch to the left (-) will lower blower motor speed in a similar manner.

MAX A/C Button

Pressing MAX A/C button will display MAX A/C and the selected temperature in display window. Blower will operate at high speed and recirculation function will be activated. Air inlet door closes to outside air.

VENT Button

Pressing VENT button will display VENT and the selected temperature in the display window. The system will operate with air directed to the panel vents and will use outside air. Compressor clutch will be off.

Panel/Floor Button

Pressing panel/floor button will show panel and floor icon, and the selected temperature, in the display window. Air will be equally distributed between panel and floor vents.

Floor Button

Pressing floor button will display floor icon, and the selected temperature, in the display window. Most air will be directed to floor ducts, with a small amount going to the window demister and defrost vents. Compressor clutch will be turned OFF.

Floor/Defrost Button

Pressing floor/defrost button will show floor/defrost icon, and the selected temperature, in the display window. Most air will be directed to floor and defrost vents, with a small amount of air going to side window demisters.

F-DEF (Front Defrost) Button

Pressing F-DEF button will show defrost icon, and the selected temperature, in the display window. Most air will be directed to defrost vents, with a small amount going to floor ducts and side window demisters.

R-DEF (Rear Defogger) Button

Pressing R-DEF button will activate rear window defogger.

A/C ELECTRONIC BLEND DOOR ACTUATOR

The A/C electronic blend door actuator is located on rear of A/C evaporator housing. A/C temperature blend door controls movement on command from the Remote Climate Control (RCC) module. Internally, an electronic circuit accepts commands from RCC module and positions A/C temperature blend door using a reversible electric motor. An integral potentiometer feeds temperature blend door position information to RCC module.

Ambient Air Temperature Sensor

Sensor contains a thermistor (temperature sensitive resistor), which measures outside air temperature and inputs signal to RCC module. Ambient air temperature sensor is located in front of condenser, on radiator support, near center of vehicle.

In-Car Temperature Sensor

Sensor contains a thermistor (temperature sensitive resistor), which measures temperature inside vehicle and inputs signal to RCC module. In-car temperature sensor is located on back of integrated control panel.

Sunload Sensor

Sunload sensor contains a photovoltaic (sunlight sensitive) diode, which measures sunlight entering vehicle and inputs signal to RCC module. Sensor is located on upper right instrument panel.

Pressing the FAN rocker switch to the right (+) will raise the blower to the desired speed. Pressing the rocker switch to the left (-) will lower the blower speed in a similar manner.

Blower Motor Speed Controller

Blower motor speed controller is a pulse width modulated unit providing variable blower speed control. It controls speed of blower by switch blower motor off and on 40,000 times per second by varying voltage signal on and off. Blower motor speed controller can also compensate for changes in battery voltage to prevent slower blower speeds at idle. Blower motor speed controller is located under evaporator housing, near blower motor.

VACUUM CONTROL MOTORS

Vacuum actuators control movement of air distribution doors. Vacuum actuators are mounted on evaporator housing. They direct system airflow as determined by RCC module signal or by manual override.

In the 5-passenger seating configuration, an additional vacuum actuator is mounted on the heater plenum. This actuator controls airflow to the rear seat A/C register.

FIXED ORIFICE TUBE

Fixed orifice tube, located in liquid line at condenser connection, creates a restriction in high side pressure line and meters flow of liquid refrigerant into evaporator core. Tube has filter screens on both ends. Fixed orifice tube is not adjustable or repairable.

A/C Compressor Clutch

In any mode in which the A/C compressor clutch operates, the compressor clutch (signal) is controlled by Constant Control Relay Module (CCRM). CCRM is located in front of engine compartment, on upper radiator support. The Powertrain Control Module (PCM) will override the RCC module commands and disengage the compressor clutch during wide open throttle acceleration.

A/C Clutch Cycling Pressure Switch

The A/C clutch cycling pressure switch is mounted on a Schrader valve on top of accumulator-drier, monitors low side pressure. If low side pressure decreases to a preset pressure, switch contacts open, preventing compressor clutch engagement. As pressure increases to a preset pressure, switch contacts close, allowing compressor clutch engagement. See A/C CYCLING SWITCH SPECIFICATIONS table. When replacing A/C cycling switch it is not necessary to discharge A/C system.

A/C CYCLING SWITCH SPECIFICATIONS

Compressor Anti-Slugging Strategy (CASS)

Liquid refrigerant may accumulate in A/C compressor under certain conditions. To alleviate damage to A/C compressor, Compressor Anti-Slugging Strategy (CASS) is utilized. CASS is initiated only under specific conditions

1. Ignition is off for more than 8 hours
2. Ambient temperature is above -4°C (25°F)
3. Battery voltage is above 8.5 volts during engine cranking

When these conditions exist, PCM will activate the A/C control relay prior to engine cranking. A/C control relay engages A/C compressor for approximately 4-15 revolutions of A/C compressor or a maximum of 2 seconds (depending upon vehicle application), allowing the liquid refrigerant to be pushed from the A/C compressor. CASS is initiated by the PCM regardless of function selector switch position.

SYSTEM TESTS

A/C SYSTEM PERFORMANCE

1. Park vehicle out of direct sunlight. Connect manifold gauge set. Start and run engine at 1500 RPM. Set A/C controls to MAX A/C and maximum cold temperature setting.
2. Set blower motor on high speed. Close doors and windows. Insert thermometer in center vent. Operate system for 10 minutes to allow system to stabilize. Measure center vent output temperature. See «A/C SYSTEM PERFORMANCE SPECIFICATIONS»(ref-62841-S36672431512001011900000) table.
3. At about 68°F (20°C) ambient temperature, high side pressures should be approximately 100-200 psi (7.0-14.1 kg/cm 2 ). Low side pressures should be approximately 24-46 psi (1.7-3.2 kg/cm 2 ).
4. As low side pressure decreases, high side pressure should increase. When A/C clutch disengages, low side pressure will increase and high side pressure should decrease. See «A/C SYSTEM HIGH SIDE PRESSURE SPECIFICATIONS»(ref-62841-S02259150952001011900000) table.

A/C SYSTEM PERFORMANCE SPECIFICATIONS

A/C SYSTEM HIGH SIDE PRESSURE SPECIFICATIONS

EVAPORATOR CORE

Note. The evaporator core is serviced as a core and housing assembly (evaporator core, internal doors, seal and door linkage are included with housing).