Alfa Romeo Repair: the wipers on the car will..., older models, connector plug

Question
the wipers on the car will always work on the fast speed but the slow speed and intermitant very rarly work and the wipers never park but then one day out of the blue they might work and be fine for about 10 minutes  

Answer
The contacts in the wiper head are corroded. Take it apart and clean them or buy a new or rebuilt unit.

You did not state model and year but the take apart is usually easy on Magnetti Marelli models.

On older models the problem could also be in the connector plug.