Hi , I have 2 Neff dishwashers. exactly 3 years after purchasing them we had the same issue, water was not getting hot, it was the Heat Pump in the machine that gave up, purchased a new one online and husband fitted it after getting instructions online on how to fit it etc, worked perfectly after that. 6 months later exact same problem in the identical 2nd dishwasher, purchased heat pump again and worked perfectly after that. May or may not be your issue but as it went in our 2nd dishwasher not long after I figure this must be a very common part to fail in dishwashers.