Why did 12v electric fail ?

We are using mains whilst on site but suddenly all lights went out.The control panel turned red with a list of all the fuses showing failed.The mains power was still working.After 5 mins everything came back on.I could hear a fan under the passenger seat . Possibly answering my own question,is it the charger overheating and re setting ?  Neuvo 2008.

It would be quite unusual for the built-in charger/power supply to overheat - typically they are rated to supply 20A continuously, and not many people will use that much on the 12V side.

I don't know the layout of a 2008 Devon at all, but I don't *think* A/S ever fitted the mains charger/power supply under the passenger seat - it may be worth a bit more investigation to see if you can identify exactly what the unit is that has a fan running?

Pip wrote:We are using mains whilst on site but suddenly all lights went out.The control panel turned red with a list of all the fuses showing failed.The mains power was still working.After 5 mins everything came back on.I could hear a fan under the passenger seat . Possibly answering my own question,is it the charger overheating and re setting ?  Neuvo 2008.

It sounds to me that the mains power had a short power outage as the fan sound that you heard was the battery charger starting up and that could indicate a failing leisure battery but it could also mean that all charge is being sent to the vehicle battery if you have an MES Control Panel above the door as I have on my Nuevo, if so then change the CHG button from VEH to HAB.
Hope this helps.