Thank you for your post. It was very useful for me. I have a dishwasher AEG Favorit 40740 Sensorlogic and after more than 10 years in service, it stops heating the water. After reading your post I open the control unit and found the same problem that you described in your post. It was very easy to identify the fault relay joint on the backside of the control unit located on the backside of the front door, behind the program and timer butons. The fault relay joint was dark and had no solder and no electrical contact. After filling the relay contact with solder and assembling everything together it worked just fine.
Without reading your post it would be much more difficult to identify the problem. Thank you.
Rui Lança (from Faro, Portugal).