Rear windscreen wiper does not work although you hear the relay ???

Hello, my loyal Elsch (V40, year 1999, 2,0T) is getting me out of my mind right now and I hope someone can help me with my suffering. After the rear windscreen wiper only worked sporadically, I removed the engine and cleaned it as described in the forum. After that it ran for about 6 months again, then it started that you didn’t hear the pump at the splash water switch (back window), but everything still works on the windshield until today. Electricity comes to the rear wiper engine and you hear the relay work, but unfortunately the rear windscreen wiper doesn’t turn any more. Had it tried then also with a replacement wiper motor, but unfortunately without success. My guess that maybe the relay has a crack or the electronics has a problem. Does someone happen to know where the relay for the rear windscreen wiper is sitting? Did someone happen to have such a problem from you and can tell me what I can try out? Thank you in advance for your feedback.