Ford Fiesta: Wipers and Washers / Wipers and Washers - System Operation and Component Description. Description and Operation

System Operation

System Diagram

Windshield Wipers

The windshield wipers operate only when the ignition is ON.

The BCM sends 2 separate signals to the wiper/washer switch (also known as the steering column multifunction switch RH ) to monitor requests for low and high speed wiper mode operation. A separate return circuit back to the BCM provides the ground path. Depending on the wiper/washer switch selection (low or high), that signal is routed to the return circuit, pulling the signal low to indicate a request for the low or high speed windshield wiper mode. Based on the input received, the BCM provides voltage to the low or high speed windshield wiper motor circuit.

The BCM also sends a signal to the windshield wiper motor to detect when the windshield wipers are in the PARK position. The BCM uses this input to determine when to cease the windshield wiper motor voltage supply so the wipers stop at the correct position on the windshield between intermittent wipes or when the windshield wipers are turned off.

Windshield Washer

The wiper/washer switch is provided voltage when the ignition is ON. The voltage passes through 2 internal switches and is routed through the BCM to the washer pump. When the washer is not activated, voltage is present on both cirucits to the washer pump. When the windshield washer switch is activated, ground is provided on one of the circuits instead of voltage, activating the washer pump.

The BCM monitors for ground on both circuits as they pass through it. When the washer switch is activated, one of the circuits is routed to ground indicating a windshield washer request. When BCM detects the request, it activates the windshield wipers in low speed mode and the washer pump for as long as the washer request is detected. The wipers wipe 4 more times after the washer pump turns off. After a brief pause, an additional courtesy wipe follows.

Mist Wipe

The mist wipe (single wipe) position of the wiper/washer switch is a momentary contact switch. When the wiper/washer switch is in the mist wipe position, it routes the signal for the low speed wiper request to the return circuit, pulling the signal low indicating a request to activate the low speed windshield wiper mode. The BCM keeps the low speed windshield wipers active for as long as it detects the request.

Intermittent Wipers

The BCM sends a signal to the wiper/washer switch to monitor the request for the intermittent wipers. When the wiper/washer switch is placed to the intermittent position, the signal is routed to the return circuit, pulling the signal low indicating a request for the intermittent wiper mode. When BCM detects the intermittent wiper mode request, it monitors a separate circuit for the interval timing.

The interval timing signal to the wiper/washer switch passes through a rheostat within the wiper/washer switch. The signal varies, based on the 6 intermittent settings. The 6 intermitting settings are:

• AUTO 1/INT 1
• AUTO 2/INT 2
• AUTO 3/INT 3
• AUTO 4/INT 4
• AUTO 5/INT 5
• AUTO 6/INT 6

Rain Sensitive Wipers (if equipped)

When equipped, the rain sensitive wiper feature replaces the intermittent wiper feature. The rain sensitive feature is active when the wiper/washer switch is in any of the 6 auto/intermittent settings. The setting closest to OFF is the least sensitive to moisture, the highest setting being the most sensitive to moisture.

The rain sensor sends data through the LIN to the BCM . Based on the data received from the rain sensor and the auto/intermittent setting on the wiper/washer switch, the system automatically activates and adjusts the wiper speed and frequency when moisture is detected on the windshield.

The rain sensitive feature can be enabled/disabled using the message center controls. When the rain sensitive feature is disabled, the windshield wipers operate in the intermittent mode.

If a fault is detected with the rain sensitive feature, the windshield wipers default to the intermittent mode. The timing of the wipers correspond to a standard intermittent setting based on the auto/intermittent sensitivity setting on the wiper/washer switch.

Wiper Activated Exterior Lamps (if equipped)

The BCM turns the exterior lamps on within 10 seconds of the windshield wipers being activated by the wiper/washer switch when the headlamp switch is in the AUTO position. Approximately 30 seconds after the windshield wipers turn off, the BCM turns the exterior lamps off.

If equipped with rain sensitive wipers, the BCM turns the exterior lamps on when the rain sensitive wipers are activated by moisture detected on the windshield when the headlamp switch is in the AUTO position. Shortly after the rain sensitive wipers are deactivated (moisture no longer detected on the windshield), the BCM turns the exterior lamps off.

Rear Window Wiper

The BCM sends a signal to the wiper/washer switch to monitor the request for the rear window wiper. When the rear window wiper switch is activated, the signal is routed to the return circuit, pulling the signal low to indicate a rear window wiper request. When BCM detects the request, it provides voltage to the rear window wiper on 2 separate circuits. One is to provide power to activate the rear wiper motor and the other is to allow the rear wiper motor to park (powered when the ignition is ON).

If the windshield wipers are off or in the intermittent mode when the rear window wiper operation is requested, the rear window wiper activates with a 10 second delay between wipes.

If the windshield wipers are in the low speed mode when the rear window wiper operation is requested, the rear window wiper activates with a 6 second delay between wipes.

If the windshield wipers are in the high speed mode when the rear window wiper operation is requested, the rear wiper operates continuously.

If the windshield wipers are operating from the rain sesitive feature, the rear window wiper activates with a 6 second delay between wipes.

The rear window wiper motor is self-parking.

Rear Window Washer

The wiper/washer switch is provided voltage when the ignition is ON. The voltage passes through 2 internal switches and is routed through the BCM to the washer pump. When the washer is not activated, voltage is present on both cirucits to the washer pump. When the rear washer switch is activated, ground is provided on one of the circuits instead of voltage, activating the washer pump.

The BCM monitors for ground on both circuits as they pass through it. When the rear window washer switch is activated, one of the circuits is routed to ground indicating a rear window washer request. When BCM detects the request, it activates the rear window wiper and the washer pump for as long as the washer request is detected. The rear wiper wipes 2-3 more times after the washer pump turns off. After a brief pause, an additional courtesy wipe follows.

Component Description

Wiper/Washer Switch

The wiper/washer switch is mounted to the steering column. The windshield wiper/washer inputs to the BCM are:

• Windshield wash
• Off
• AUTO 1/INT 1
• AUTO 2/INT 2
• AUTO 3/INT 3
• AUTO 4/INT 4
• AUTO 5/INT 5
• AUTO 6/INT 6
• Low
• High

The rear wiper/washer inputs to the BCM are:

• Off
• On
• Rear window wash

Front Wiper Motor

The windshield wiper motor contains a 2-speed motor and a wiper park switch. The BCM controls the windshield wiper motor by activating the windshield wiper on/off and low/high speed relays when the ignition is on.

The BCM monitors the windshield wiper park switch. Based on this input, the BCM parks the wipers on the lower portion of the windshield when the wipers are turned off and between wipes when the windshield wipers are in the intermittent mode.

There is a mechanical linkage between the windshield wiper motor and the wiper arms.

Washer Pump

The washer pump is controlled by the BCM . The front and rear washer system share the same washer reservoir and a bi-directional washer pump. The washer pump delivers washer fluid to the windshield when the BCM activates the windshield washer relay (internal to the BCM ), which provides voltage to the washer pump. Ground for the washer pump is provided through the rear washer relay (also internal to the BCM ). When activated, the washer pump delivers washer fluid to the windshield.

When the BCM energizes the rear washer relay, the rear washer relay provides voltage to the washer pump. Ground for the washer pump is provided through the windshield washer relay. When activated, the pump delivers washer fluid to the rear window.

Rain Sensor

The rain sensor uses an infrared beam to optically sense water on the windshield. The intensity of the reflected beam is measured and compared to the intensity of the transmitted beam. If there is water on the surface of the windshield, the beam distorts, reducing the intensity of the beam. If the beam is not reflected completely, it is interpreted as rain on the windshield and the windshield wipers are activated.

A gel-type lens is used as the interface between the rain sensor and the windshield. If the lens is missing or damaged, the rain sensing wipers may be inoperative or not operate correctly. The rain sensor gel-type lens cannot be replaced separately on a rain sensor of this type.

Rear Wiper Motor

The rear window wiper motor contains a single speed motor. When the BCM momentarily provides voltage to the rear window wiper motor, the rear window wiper activates. A separate power circuit is used to continue the rear window wipe and park the rear window wiper.