Truma W45H error code

[Anjistar]

On a Fiat Ducato PVC.

It works fine plugged into EHU, but if I try to turn it all down or off when off-grid I get the error code.

Truma Fault codes give these options and solutions:
No 230 V operating voltage: Restore 230 V operating voltage BUT it's supposed to still work when not on EHU.

230 V fuse defective: Replace 230 V fuse (see Combi operating instructions) BUT what has blown the fuse

Overheating protection has been triggered: Reset overheating protection (see Combi operating instructions) BUT again, what has caused the overheating.

I could just work through these, but it won't help me understand what's causing the fault, so it will presumably just happen again.
There's nothing in the instruction manual to help an electrically-challenged person know how to set it up for when the van is parked up for a few days between trips, so if anyone could help out, I'd be grateful!

 

[jezport]

Are you turning the fuel source to gas with the heating off before you disconnect the EHU? If you dont it will trigger the error warning.

 

[Anjistar]

Are you turning the fuel source to gas with the heating off before you disconnect the EHU? If you dont it will trigger the error warning.

Aha - that might be it. Thank you, Jezport.

So, of the four options on the panel - Van, Water, Fuel source, Fan, I switch the first two Off, then change the fuel source to gas?

I didn't realise the boiler doesn't work off the leisure battery.

I wish the instructions had a bit more explanation to them - if you don't do this, then this will happen, because...