Some classic British cars such as the MG MGA or Triumph TR2 came with a single speed DR2 wiper motor. When encountering rain of various intensity, the single speed is just not appropriate 90% of the time. Here is a fully customisable, Arduino based, multi frequency controller that is non-destructive and fully reversible for your car. Just wire it between the original switch and the motor and you're ready to go.
Follow the project logs (starting here) for a complete description of the controller, schematics, PCB layout, and final result (video above).
Feel free to ask any question, I'll do my best to answer.