HOTPOINT FDW70P DISHWASHER A10 ERROR CODE

Hi, my hotpoint fdw70p dishwasher is showing an error code A10 which according to the trouble shooting guidelines on the hotpoint website its a fill valve problem.
I have changed the fill valve and the code is still showing.
The error is occuring 2 minutes into starting any cycle except a pre wash cycle which it completes fine.
Can anyone shed some light on this because hotpoint don't have a technical team and want to send an engineer out to me which i'm not paying for when it could end up being something really trivial which I can correct myself.
I can't understand how it could be the fill valve due to it completing a pre wash cycle however i changed it anyway and as said before still no joy.

HELP!!!!

heater open circuit . very common .

Is there any simple fix for it? Where would i start? How come it will do a full pre wash cycle if this is the problem?

prewash is a cold wash. heater comes on after that and then errors out .heater will cost about 30 quid about a ten min job to do .

quick add to this mine has the same fault but my machine is hot so water seems to have come in and pumped out ....but when the a10 code shows there is the sound of what seems to be a water pump trying to do somthing