It could be a dryjoint on the controller PCB. This was the case with my dishwasher which I've just finished fixing. You need to dismantle the control unit in the door and look at the underside of the PCB, right under the relay. If you find a scorched spot on the PCB then this is the most likely problem. Take a look at http://www.ukwhitegoods.co.uk/modules.php?name=Forums&file=viewtopic&t=13070&postdays=0&postorder=asc&start=15
for photos of the relay and PCB underside. Problem was reported for an AEG Favorit 40850 but the solution also applies to the Zanussi DE6850. Hope this helps!
teacherboy
March 2007