Land Rover Discovery Owners & Service Manuals

Land Rover Discovery: Windshield Wiper Fast/Slow/Single Wipe - Operation

Land Rover Discovery (2009–2016) Service Manual / Body / Wipers and washers / Wipers and Washers / Windshield Wiper Fast/Slow/Single Wipe - Operation

OPERATION

Slow Wipe

When the driver moves the wipers and washers control switch to the slow wipe position, the Central Junction Box (CJB) detects a Local Interconnect Network (LIN) bus message and energizes the wiper on/off relay in the Battery Junction Box (BJB). Power flows to the relay contacts of the fast/slow wiper relay in the BJB which supplies power to the windshield wiper motor via a resistor in the motor. The motor will operate at slow speed until fast speed is selected or the On/Off relay is de-energized, removing the power to the windshield wiper motor.

Fast Wipe

When the driver moves the wipers and washers control switch to the fast wipe position, the CJB detects a LIN bus message and energizes the wiper on/off relay in the BJB. Power flows to the relay contacts of the fast/slow wiper relay in the BJB. The CJB provides the ground path for the coil of the fast/slow wiper relay, moving the relay contacts to supply power directly to the windshield wiper motor, bypassing the resistor used for the slow wipe.

The windshield wiper motor will operate at fast speed until slow speed is selected or the relays are de-energized, removing the power to the windshield wiper motor.

Single Wipe

When the driver moves the wipers and washers control switch to the single wipe position, the CJB detects a LIN bus message and energizes the wiper on/off relay in the BJB. Power flows to the relay contacts of the fast/slow wiper relay in the BJB. The motor will operate at slow speed until the wipers and washers control switch is released from the single wipe position. The on/off relay is de-energized, removing the power to the windshield wiper motor.

WINDSHIELD WIPER PARK

The windshield wiper park switch is integral with the windshield wiper motor. The park switch ensures the windshield wipers return to the park position when the windshield wipers are switched off on the wipers and washers control switch.

The park switch is part of the windshield wiper motor gear wheel. When the windshield wipers move from the park position, the park switch contacts are open. When the windshield wiper becomes near to the park position the park switch contacts are closed and a ground path to the CJB is completed.

When the CJB receives a LIN bus signal from the wipers and washers control switch that a wiper operation is selected, the park switch status is continually monitored by the CJB. If the wipers and washers control switch is moved to the off position, when the CJB next senses the ground signal from the park switch, it will remove the power supplies via the wiper on/off relay, stopping the windshield wipers in the park position.

Windshield wiper intermittent function - Operation

NOTE:

On vehicles without a rain/light sensor, only the intermittent function is available. On vehicles with a rain/light sensor the intermittent function can be selected using the Instrument Cluster (IC) menu to disable the automatic wipers function.

When the driver moves the wipers and washers control switch to the intermittent wipe position, the Central Junction Box (CJB) detects a Local Interconnect Network (LIN) bus message and energizes the wiper on/off relay in the Battery Junction Box (BJB). Power flows to the relay contacts of the fast/slow wiper relay in the BJB. The motor will operate at slow speed until the On/Off relay is de-energized, removing the power to the windshield wiper motor.

Simultaneously, the CJB monitors the LIN bus signal from the intermittent delay adjustment switch. Depending on the adjustment switch position, the CJB will operate the windshield wipers for one single wipe. After a time period relating to the adjustment switch position, the CJB will repeat the process until the driver selects wipers off on the wipers and washers control switch or a different windshield wiper selection is made.

Delay Timers

The delay periods in seconds relating to the switch positions are as follows:

  • 21 seconds
  • 15 seconds
  • 11 seconds
  • 7 seconds
  • 4 seconds
  • 2 second.

WINDSHIELD WASHERS

When the driver moves the wipers and washers control switch to the windshield wash position, the CJB energizes the front washer relay. Power is supplied through the relay contacts to the front washer pump. The ground path for the pump is provided through the contacts of the de-energized rear washer relay. Both front and rear washer relays are located in the CJB.

When windshield washer operation is requested, the windshield washers will operate. The CJB will delay windshield wiper operation for 250 ms after the driver has operated the wipers and washers control switch in the windshield wash position.

The CJB will operate the windshield wipers for as long as the driver operates the wipers and washer control switch in the windshield washer position. The washer pump will only be powered for a maximum of 10 seconds. After the switch is released, the CJB will operate the wipers for two full cycles. After a 4 second delay, the CJB will operate the windshield wipers for one full cycle to remove any residual washer fluid from the windshield.

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