Parking position of windscrren wipers varies significantly

[Yorkshire Engineer]

Depending on the amount of rain wipers park at different places.
Cause: dynamic braking not operational. Wipers are being slowed simply by friction. There is significant kinetic energy in the motor rotor to dissipate.
Solution: replace wiper control module.
Background: The wiper motor drives what appears to be a double reduction gearbox. As such the motor rotates at a significant rpm and has a lot of kinetic energy. The double gearbox keeps the size of motor down but the stored energy does cause a design problem.
The wiper switch does not control the wipers directly. Instead it sends commands to a module that manages intermittent wipe, wash-wipe and parking. There is a sensor within the gearbox attached to the end of the wiper motor that indicates the location of the parking position. When the wiper switch is moved to off and this sensor activates, the module removes drive power from the motor and shorts the motor terminals together. This results in the motor stopping within perhaps a tenth of a second and within a repeatable distance. Several amps of current flow during this violent dynamic brake and contacts can become damaged.
I think the module is located on the rear of the fuse box.

Should the wipers not stop and to continue to wipe for a random number of times before parking this would suggest that either the parking sensor is wearing out or the connector needs disconnecting and re-connecting to clean the contacts.

It would appear that it is not possible to adjust the parking position.

CB radio gear placed on the bonnet could cause a mal-function.

The wiper motor/gearbox has considerable torque. Take care to keep body parts away from the linkage. It could easily break a finger.