PRE-RELEASE
Windscreen wiper operation, detailed description
| Windscreen wiper operation, detailed description |
The windscreen wiper assembly is located under the cover beneath the windscreen. The wipers are controlled by the stalk-switch to the right of the steering column. The assembly comprises a motor, two wiper arms and a crank mechanism which converts the motor rotation into the reciprocating motion of the wipers. The motor has a built-in thermoswitch which trips if the wipers are activated and the blades are jammed (e.g. frozen to the windscreen).
The wiper stalk-switch selection positions:
| A. |
Low speed
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| B. |
High speed
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| C. |
Single stroke/service position.
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| D. |
Intermittent
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| E. |
Washing
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| F. |
Wipers parked
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The wiper stalk-switch (61) is integrated with the CIM (703). The CIM transmits a message on the bus giving the position of the stalk-switch. Windscreen wiping is only possible when the ignition switch is in either the OFF or the ON position.
| Low speed (A) |
When low speed is selected on the wiper stalk-switch the CIM (703) transmits a "Windscreen wiper, stalk-switch, position LOW SPEED" message on the bus. The message is processed by the UEC (342) which activates relay 83 and the wiper motor (62F) is connected to the voltage supply. The UEC (342) supplies B+ on pin 30(F) which is connected to pin 4 on the wiper motor (62F). Pin 3 on the wiper motor is connected to ground. If the ignition is switched off when the wiper blades are not in the parking position the UEC (342) continues to run the motor until the parking position is reached.
| High speed (B) |
When high speed is selected on the wiper stalk-switch the CIM (703) transmits a "Windscreen wiper, stalk-switch, position HIGH SPEED" message on the bus. The message is processed by the UEC (342) which activates relays 83 and 709 and the wiper motor (62F) is connected to the voltage supply. The UEC (342) supplies B+ on pin 29 (F) which is connected to pin 1 on the wiper motor (62F). Pin 3 on the wiper motor is connected to ground. If the ignition is switched off when the wiper blades are not in the parking position the UEC (342) continues to run the motor until the parking position is reached.
| Single stroke and service position (C) |
Single stroke
When the windscreen wiper stalk-switch is moved to the spring-loaded, single stroke position, the CIM (703) transmits the bus message "Windscreen wiper, stalk-switch, SPRING-LOADED POSITION", on condition that the ignition is ON. The message is processed by the UEC (342) which activates relay 83 and the wiper motor (62F) is connected to the voltage supply. The UEC (342) supplies B+ on pin 30(F) which is connected to pin 4 on the wiper motor (62F). Pin 3 on the wiper motor is connected to ground.
Service position
When the windscreen wiper stalk-switch is moved to the spring-loaded, single stroke position, the CIM (703) transmits the bus message "Windscreen wiper, stalk-switch, SPRING-LOADED POSITION", on condition that the ignition is in the LOCK position. The UEC(342) activates the wiper motor so long as the stalk-switch remains in the single stroke position but for no more than one stroke.
This function is only possible if the spring-loaded position is selected within 16 seconds of the ignition having been switched off. Subsequent activation is possible so long as the VEC(342) is awake, normally for a period of 8 minutes.
| Intermittent (D) |
When intermittent wiping is selected on the wiper stalk-switch the CIM (703) transmits a "Windscreen wiper, stalk-switch, position INTERMITTENT" message on the bus. The message is processed by the UEC (342) which activates relay 83 and the wiper motor (62F) is connected to the voltage supply. The UEC (342) supplies B+ on pin 30 which is connected to pin 4 on the wiper motor (62F). Pin 3 on the wiper motor is connected to ground. If the ignition is switched off when the wiper blades are not in the parking position the UEC (342) continues to run the motor until the parking position is reached. The intermittent wiping interval can be set to between 2 and 15 seconds.
| End position contact. |
The wiper motor has an inbuilt contact which serves to protect the motor if the wiper blades are obstructed and is used to establish the wiper parking position and the number of wipe cycles during windscreen washing.
Obstruction protection
If the wiper arms are obstructed the status of the end position contact will not change. If the status is static for more than 20 s when the output signal to the wipers is activated, the UEC (342) will then de-activate the signal.
Wipers parked
The end position contact is used to ensure that the wipers park in the correct position. The contact is closed when the wiper mechanism is in the parking position.
The end position contact is also used by UEC (342) to establish the number of wipe cycles when wiping in conjunction with windscreen washing.
The end position contact is connected to the wiper motor pin 2 which is in turn connected to pin 11 (F) on the VEC (342). When the wipers are in the parking position the contact is closed and the UEC pin 11 (F) is thus grounded.
