Blown a fuse?

I've been using a three socket version of that adaptor fixed to my Land Rover for years with no problem. That socket design was originally intended for a plug-in cigar lighter, long before there were 12v accessories to plug into it. They now seem to be made to a simpler, cheaper design that does not favour repeated disconnection.

But back to the OPs problem - what I read from the text is that there is a battery, seperate from the habitation battery, that a previous user has "hard wired" this adapter into. I don't know the vehicle type, but this might actually be the cranking battery. Anyway, I see it as nothing to do with the fitted systems but a complete add-on, perhaps as a source of power when the other battery goes flat.

My suggestion for Miranda, if she wants to continue to have the option of power from the under-seat battery, is to junk that adaptor and fit (or have fitted for her) a good quality socket with decent size wires, fuses and connectors. There is a range available from e-Bay (and others) that have 12v and USB outlets and a volt meter in a bezel for (today) £8.16. Fitting it to the vehicle somewhere will avoid the problem with these flying adaptors that someone trips over the wire and it all comes apart.

good advice from all above. from reading M's posts I'm guessing she's also camping (or will be) a bit off grid....the odd festival, rally?

this will certainly keep costs down for someone sing their van to work from....sites every night at £20 will soon eat a lot of that hard earned.

so, I would suggest a couple of things....and the first one would be a solar panel that charges the leisure and vehicle battery allowing you to stay away from EHU and keep costs down...

this will also necessitate a good reliable gas supply, for fridge, heating, hot water......and that kettle

added to that, try and get as much of your electrical 'stuff' working from 12v (phone/tablet charging etc) however a small inverter cans still be very useful, BUT it needs to wired in directly to the leisure battery and be fused.

good luck

The socket only looks like the one in the pic, the wire has been threaded through a lot of the MH itself so it's possible I've missed spotting the fuse. I'll have another look along the wire for one. 

I've checked it isnt working by plugging about a million 12v and USB plugged items in which don't work on that socket, but do work on another 12v socket in the MH

I've checked it isnt working by plugging about a million 12v and USB plugged items 

I'm sure that your parents also told you millions of times not to exaggerate!