Principles Of Operation

Wipers and Washers

Principles of Operation

If equipped with automatic headlamps, the Smart Junction Box (SJB) will illuminate the exterior lamps, including the parking lamps, when the front wipers are on for more than 10 seconds and the headlamp control is in the AUTOLAMP position. When the wipers are turned off, the exterior lamps will remain on for 30 seconds before turning off.

High-Speed Windshield Wipers

When the multifunction switch is set to the HIGH-speed position, it supplies ground to the high/low-speed relay coil and the run/park relay coil, which causes the windshield wiper motor to operate at high speed. During HIGH-speed operation only, both the high/low-speed relay coil ground and the run/park relay coil ground are controlled directly by the multifunction switch. This differs from LOW-speed or INTERMITTENT operation when the run/park relay coil is controlled by the microprocessor. When the switch is placed in the OFF position, the motor continues to operate until the motor returns to the PARK position and the internal Hall-effect sensor senses the motor magnet. The output to the run/park relay deactivates the relay and disconnects the voltage to the motor.

Since the high/low relay coil and the run/park relay coil are both controlled by a hard-wired circuit to the multifunction switch, the windshield wipers will still operate in high-speed mode if the internal windshield wiper module fails, but will not automatically park when the multifunction switch is turned to the OFF position.

Low-Speed Windshield Wipers

When the multifunction switch is set to the LOW-speed position, it supplies ground to the internal windshield wiper motor module low-speed input and the windshield wiper motor operates at low speed. During LOW-speed operation, the internal run/park relay is activated by the microprocessor and supplies 12 volts to the low-speed brush of the windshield wiper motor. The run/park relay coil ground is controlled by the internal windshield wiper motor module based on inputs received from the multifunction switch. When the switch is placed in the OFF position, the motor continues to operate until the motor returns to the PARK position and the internal Hall-effect sensor senses the motor magnet. The output to the run/park relay deactivates the relay and disconnects the voltage to the motor.

Since the run/park relay is controlled by the internal windshield wiper motor microprocessor, the wipers will only operate in high-speed mode if the internal windshield wiper motor module fails, and will not automatically park when the multifunction switch is turned to the OFF position. This is due to the run/park and high/low relay coils being directly hard-wired to the switch in high speed. The diode prevents current flow through the high/low relay coil so the relay remains in the normally closed LOW-speed position.

Intermittent Speed Windshield Wipers

When the multifunction switch is set to the INTERMITTENT position(s), it supplies ground to the windshield wiper motor module inputs and the windshield wiper motor operates in intermittent mode. During INTERMITTENT operation, the windshield wiper motor activates the run/park relay coil which sends voltage through the high/low relay. The high/low relay remains deactivated, supplying the voltage to the low-speed brush of the windshield wiper motor. The windshield motor continues to operate until the internal Hall-effect sensor senses the magnet (PARK position) and deactivates the run/park relay, which disconnects voltage from the wiper motor. The windshield wipers remain parked until the windshield wiper motor module completes a time-out and then repeats the intermittent windshield wiper cycle.

Wiper Activated Headlamps (If Equipped with Autolamp System)

If equipped with automatic headlamps, the SJB will illuminate the exterior lamps within 10 seconds, when the wipers are on and the headlamp control switch is in the AUTOLAMP position. When the wipers are turned off, the exterior lamps will remain on for 30 seconds before turning off.

Speed Dependent Windshield Wipers

The speed-dependent feature increases the frequency of wiping to compensate for the extra moisture that accumulates on the windshield as the vehicle speed increases, when the multifunction switch is in any intermittent setting except the INT 1 position. The windshield wiper module receives Vehicle Speed Sensor (VSS) information directly from the PCM. As vehicle speed increases, the speed-dependent feature gradually shortens the delay between wipes.

The speed-dependent feature is easiest to verify in the INT 2 position. With the vehicle at a standstill and the multifunction switch in the INT 2 position, the wipers should operate once every 10 seconds. As vehicle speed increases, the delay between wipes will gradually shorten. For example, by the time the vehicle reaches 100 km/h (62 mph), the wipers should operate every 5 seconds. Speed dependent operation is similar in INT 3, INT 4 and INT 5 modes.

Intermittent Rear Window Wiper System

When the multifunction switch is set to the rear INTERMITTENT position(s), it supplies ground to the rear window wiper motor module input and the wiper operates in intermittent mode. During INTERMITTENT operation, the rear wiper motor momentarily activates the rear window wiper relay (internal), which sends voltage to the motor. Once the rear window wiper motor is activated, the internal run/park switch connects voltage to the motor, keeping it operating. When the rear window wiper motor returns to the PARK position, the run/park switch disconnects voltage internally from the wiper motor input, reconnecting it to the rear window wiper motor module output. The rear window wiper remains parked until the rear window wiper motor module completes a time-out and then repeats the cycle.

Washer System - Explorer Sport Trac

When windshield WASH is selected on the multifunction switch, the windshield wiper motor module activates its integral washer relay which sends voltage to the washer pump to direct fluid to the windshield.

Washer System - Explorer

The front and rear washer system share the same washer reservoir and washer pump. The front and rear wiper motor modules each contain an integral washer relay that supplies a ground path for the washer pump whenever they are inactive. When windshield WASH is selected on the multifunction switch, the windshield wiper motor module activates its integral washer relay, which sends voltage to the washer pump to direct fluid to the windshield. When rear WASH is selected on the multifunction switch, the rear wiper motor module activates its integral washer relay to send voltage to the washer pump to direct fluid to the rear window.

Software Safe Mode

The windshield wiper motor defaults to software safe mode when the run/park sensor does not sense the Hall-effect magnet inside the wiper motor. This can be caused by an obstruction of the windshield wipers, a binding linkage or loss of the Hall sensor signal. The motor continues to operate in a high/low-speed condition, and when turned off, the wipers immediately park on the windshield. If necessary, the wipers can be turned ON and OFF until they return to the PARK position.

Windshield Wiper Circuit Function Table:

Rear Wiper Circuit Function Table: