DESCRIPTION AND OPERATION

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1 Your Current Vehicle: 1998 Ford Explorer Top / Heating, Ventilation, & Air Conditioning / Control Components / DESCRIPTION AND OPERATION DESCRIPTION AND OPERATION SECTION : Control Components 1998 Explorer/Mountaineer Workshop Manual DESCRIPTION AND OPERATION Procedure revision date: 02/16/2000 Control Components Manual The manual climate control system heats or cools the vehicle interior depending on the function selector position selected. Function selector position determines heating or cooling and air distribution. The blend control setting determines air. The manual climate control components are used to: select air inlet source ( or recirculated). select speed. select discharge air ( blend). select discharge air location (defrost, panel, floor). select compressor clutch operation. Electronic Automatic Temperature Control With the use of a microcontroller, the electronic automatic control (EATC) module analyzes input from the following major sources: /8

, function and selection (made by the vehicle occupants) in-vehicle ambient sunload vehicle speed engine coolant Using these inputs, the microcontroller determines the correct conditions for the

2 , function and selection (made by the vehicle occupants) in-vehicle ambient sunload vehicle speed engine coolant Using these inputs, the microcontroller determines the correct conditions for the following outputs: clutch engagement speed air blend door position panel/floor door position panel/defrost door position air inlet door position Component Locations Click to Enlarge /8

3 Item Part Number Description Manual control assembly Electronic automatic control module 3 19D888 Automatic control sensor hose and elbow (EATC only) 4 19E663 sunload sensor (EATC only) 5 18A318 Vacuum control (air inlet door) 6 19E616 electronic door actuator 7 18A318 Vacuum control (panel/defrost door) Heater switch resistor 9 19E702 ambient air sensor and bracket (EATC only) 10 19E624 speed control (EATC only) 11 18A318 Vacuum control (floor/panel door) Control System Inputs Manual Climate Control Assembly The climate control assembly has three system controls: The heater function selector switch combines a vacuum selector valve with two electrical switches to supply battery positive voltage (B+) to the clutch circuit and the control circuit. The selection is accomplished with a potentiometer connected to the electric blend door actuator that controls positioning of the blend door. Movement of the control knob (18519) from COOL (blue) to WARM (red) causes a corresponding movement on the air control door and determines the that the system will maintain. The switch controls speed by adding or bypassing resistors in the heater switch resistor (18591). Control System Inputs EATC Climate Control Assembly The electronic automatic control (EATC) module, located in the instrument panel, has the following features: 11 push buttons a speed override thumbwheel for manual input a vacuum fluorescent display for displaying set, function and diagnostic trouble codes (DTCs) an on-board diagnostic (OBD) feature to supply the technician with diagnostic trouble codes (DTCs). These DTCs direct the technician to the inoperative component /8

4 Ambient Air Temperature Sensor The ambient air sensor and bracket (19E702): is located in front of the condenser core (19712) near the center of the vehicle. contains a thermistor which measures the of as a resistance and sends that reading to the electronic automatic control assembly. In-Car Temperature Sensor The in-car sensor operates in the following manner: A thermistor in the in-car sensor measures air inside the passenger compartment. An automatic control sensor hose and elbow (19D888) is connected between the plenum assembly in-car sensor. The automatic control sensor hose and elbow takes air from the plenum assembly air stream to create a suction in the in-car sensor. The suction draws in-vehicle air into the in-car sensor and across the thermistor. Sunload Sensor The sunload sensor (19E663): is located on the top of the instrument panel (04320). contains a photovoltaic diode that is sensitive to light. has some unspecified resistance across the terminals depending upon the amount of light reaching the photovoltaic diode; therefore the only test that can be carried out is for an internal short circuit. Control System Outputs Manual Blower Motor Switch Resistor The heater switch resistor has the following features: The assembly is located on the evaporator housing in the engine compartment. Three resistance elements are mounted on the resistor board to provide four Depending on the heater switch position, series resistance is added or bypassed in the circuit to decrease or increase speed /8

5 An overheating protective device (thermal limiter) will open the resistor coil circuit when the reaches 121 C (250 F) interrupting the operation in all speeds except HI. The thermal limiter cannot be reset and is not serviceable. Control System Outputs EATC Blower Motor Speed Control The speed control is located on the evaporator housing in the engine compartment. The function of the speed control is to convert low power signals from the electronic automatic control module to a high current, variable ground feed for the (18527). The speed is infinitely variable and is controlled by the electronic automatic control module software. A delay function provides a gradual increase or decrease in speed under all conditions. Electric Blend Door Actuator The electric blend door actuator is located on the plenum assembly. Its function is to move the air blend door on command from the control assembly. The electric blend door actuator contains a reversible electric and a potentiometer. The potentiometer wiper is connected to the actuator output shaft and moves with the output shaft to indicate the position of the air blend door. A 5 volt signal is applied to the ends of the potentiometer. The voltage available at the wiper indicates the position of the potentiometer. The expressed value of the actuator wiper voltage is sent to the electronic automatic control module and is matched with the wiper voltage of the module potentiometer. The control module then drives the actuator in whichever direction is necessary to make the actuator wiper voltage agree with the control module wiper voltage. EATC SYSTEM RESPONSE Control Assembly Selection Air Temperature Blend Door Panel/Floor Door Panel/Defrost Door Air Inlet Door Blower Motor (Unless Manually Overridden) /8

6 OFF AUTO MAX VENT Remains fixed a ccording to The air blend door is in the heat position when s are cool. The air blend door is in the position when s are hot. Fixed in PANEL floor during heating. Air to the panel during cooling. Air to both between heating and cooling. panel. panel. Fixed in windshield defroster hose nozzle during heating. Air to the panel during cooling. PANEL PANEL Fixed in RECIRC Recirculates air when maximum air conditioning is required. Otherwise. RECIRC Blower Motor OFF speeds when the engine coolant 49 C (120 F) or is required. Low speed when the engine coolant is below 49 C (120 F) and heating is required. Disabled disabled /8

7 PNL-FLR FLOOR FLR-DEF panel and floor. Air to floor. panel and floor. panel. PANEL disabled. a If the engine coolant fails to reach 50 C (122 F) after 3 1/2 minutes of operation, the speed will increase panel/floor door will shift from the defrost position to the floor Copyright 2016 by Chilton, an imprint of Cengage Learning /8

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5/12/2018 Climate Control - Control Components - Description and Operation 2009 Ford F-150 MotoLogic

5/12/2018 Climate Control - Control Components - Description and Operation 2009 Ford F-150 MotoLogic 2009 F-150 Subarticles Report a problem with this article Electronic Manual Temperature Control (EMTC) Dual-Zone Electronic Automatic Temperature Control (EATC) SECTION 412-01: Climate Control 2009 F-150