This is weird...
4 year old dishwasher tripped out with an F70 error, pump running flat out error.
Water had drained and pump was just sucking air. So this usually means the drip pan bottom plate has got water in it and triggered the float switch, which is the white circle on the left here:
There was water in the drip pan and the polystyrene on the float was wet
- so that's why it tripped.
What I couldn't locate was any source for the leak - apart from a mummified slug and a few spider webs, it was as clean as a whistle - so evidence of any drips, mineral encrustations etc on any water bearing components.
Was wondering if it could have been condensation over a long period - it wouldn't take much water to trip the float as it's in a little well in the pan. The pan was sitting in contact with a cold slate floor. I've unscrewed the feet a bit now so it should be off the floor slightly.
Been working all day since...