Rear-wheel drive VW Passat, manufactured in 1998

Can someone tell me how the rear wiper is controlled (voltage pulse or switching to ground)?
My windshield wiper is broken and no longer works. The motor itself functions, but the control unit is heavily corroded due to water damage.
Four wires connect to the wiper motor (terminal 31, terminal 15, INT, and ground). Since only surface-mount components are on the circuit board, I'm wondering if these components are available for individual purchase.


Thank you for your help!

Is that a Passat 3B or what?

Then the wiper motor is only available as a complete unit.