Ford F150 Pickup. Instruction — part 1662

Fig. 6: Identifying Blower Motor Thermal Limiter
Courtesy of FORD MOTOR CO.

The heater blower motor switch resistor has the following features:

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The assembly is located on the passenger side of the plenum assembly behind the glove compartment
(06010).

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Three resistance elements are mounted on the resistor board to provide four A/C blower motor speeds.

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Depending on the heater blower motor switch position, series resistance is added or bypassed in the A/C
blower motor circuit to decrease or increase A/C blower motor speed.

2003 Ford Pickup F150

2003 HVAC Control Components - F150 Pickup

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An overheating protective device (thermal limiter) will open the resistor coil circuit when the temperature
reaches 121°C (250°F), interrupting the blower motor operation in all speeds except HI.

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The thermal limiter cannot be reset and is not serviceable.

Electronic Automatic Climate Control (EATC)

The EATC system heats or cools the vehicle interior depending on the function and temperature selected. The
function selection determines heating or cooling and air distribution. The temperature blend control setting
determines air temperature.

The EATC components are used to:

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automatically determine the climate control settings based on the temperature selected and ambient
conditions (AUTO mode).

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select the air inlet source (outside or recirculated).

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select the blower motor speed.

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select the discharge air temperature (temperature blend).

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select the discharge air location (defrost, panel, floor).

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select the A/C compressor clutch operation.

EATC Control System Inputs

Climate Control Assembly

The EATC module, located in the instrument panel, has the following features:

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a blower speed override for instruction input.

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a vacuum fluorescent display for displaying set temperature, ambient temperature, function and
diagnostic trouble codes (DTCs).

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an on-board diagnostic (OBD) feature to supply the technician with diagnostic trouble codes (DTCs).
These DTCs direct the technician to the inoperative component.

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can be switched between C° and F° display readings by pressing the MAX A/C and DEFROST buttons
simultaneously for at least 1 second.

A/C Ambient Air Temperature Sensor

The A/C ambient air temperature sensor and bracket:

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is located in front of the A/C condenser core near the center of the vehicle.

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contains a thermistor which measures the temperature of outside air as a resistance and sends that reading
to the EATC module.

In-Car Temperature Sensor

2003 Ford Pickup F150

2003 HVAC Control Components - F150 Pickup

The in-car temperature sensor operates in the following manner:

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A thermistor in the in-car temperature sensor measures air temperature inside the passenger compartment.

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An automatic temperature control sensor hose and elbow is connected between the plenum assembly and
the in-car temperature sensor.

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The automatic temperature control sensor hose and elbow uses air from the plenum assembly air stream
to create a suction at the in-car temperature sensor.

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The suction draws in-vehicle air into the in-car temperature sensor and across the thermistor.

A/C Sunload Sensor

The A/C sunload sensor:

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contains a photovoltaic diode that is sensitive to light.

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supplies the EATC module with information indicating sunload.

EATC Control System Outputs

A/C Blower Motor Speed Control

The A/C blower motor speed control is a pulse width modulated (PWM) type which provides variable blower
speed control of the blower motor. The A/C blower motor speed control is controlled by switching the control
signal voltage of 5 volts OFF and ON 2,000 times per second. By varying the ratio of time on (+5 volts) to time
off (0 volts), the EATC module tells the A/C blower motor speed control how fast the blower motor should run.
The A/C blower motor speed control has the following features:

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Has circuitry to protect the blower motor from burning out in the event of a locked rotor condition.

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Can compensate for changes in battery positive voltage (B+) which prevents the blower speed from
slowing down when the engine is idling and will provide up to a maximum of 30 amperes for blower
motor operation with battery voltages between 10 and 16 volts.

DIAGNOSIS AND TESTING

CONTROL COMPONENTS

Refer to CLIMATE CONTROL SYSTEM .

REMOVAL AND INSTALLATION

CLIMATE CONTROL ASSEMBLY - EATC

Removal and Installation

1. Disconnect the battery ground cable.

2. Detach the center instrument panel finish panel.

2003 Ford Pickup F150

2003 HVAC Control Components - F150 Pickup

1. Rotate the center instrument panel finish panel vents inward.

2. Through the vent openings, grasp the center instrument panel finish panel and pull outward.

3. Detach the center instrument panel finish panel.

Temperature Blend Door Actuator

The A/C electric blend door actuator is located on the plenum assembly.

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Its function is to move the air temperature blend door on command from the control assembly.

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The A/C electric blend door actuator contains a reversible electric motor 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 temperature blend door.

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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 EATC module and is compared to the desired wiper voltage determined by the EATC
module. The control module then drives the actuator motor in whichever direction is necessary to
make the actuator wiper voltage agree with the desired wiper voltage.

Fig. 7: View Of Detaching Center Instrument Panel
Courtesy of FORD MOTOR CO.

2003 Ford Pickup F150

2003 HVAC Control Components - F150 Pickup