Re: Bosch Classicxx scs43c12gb/08 D/Washer
The Instantaneous water heater has a motorised ‘water point’ device which alternates the flow from the top to the bottom spray arms every 50 seconds. (5 second changeover). Take the top spray tube assembly away from its coupling and observe where the green cam disc is positioned. Running the machine during a wash cycle should allow you to stop it and see if it rotates or has stuck on the top spray position?
If it doesn’t = New Heater Unit 😉