The main wiring to the windscreen wipers, chances are they are not connected to any MCU. I actually build windscreenwiper relays for cars that have windscreenwiper switches with only 3 positions (off, on, fast) that do not require an extra switch. They are meant for oldtimer cars that don't have interval windscreenwiper relays, but in which you don't want to add an extra switch in the dashboard.