I tried to fit a smart-screen relay (
About Smartscreen) that I purchased some time ago. Unfortunately no joy getting it to run. After that I tried a hella relay I had lying on shelf (Hella 5WA 001 871-041) and that one was very easy to fit. Just connect the hella relay with +12v and ground, connect terminal 53s on the relay with the black/purple wire coming from the switch and connect terminal 53m on the relay with terminal 53 on the wiper motor (where the black purple wire was connected). That's all. Timing can be adjusted by turning the knob on the relay.