The electrics in the caravan is coming on great at the moment with just the blower fan in the heater not working and the fridge not working on 12v am really happy with the progress 😀
the fridge will only work on 12v when its connected to your car and the engine is running above 1500 revs, the fan for the heater will only work if you have a fully charged leisure battery in place
Apologies if stating the 'bleeding obvious' to someone knowledgeable, but an oft made mistake of new to caravans folk is that the fridge ONLY works on 12V supplied from the tow vehicle via the towbar electric socket, NOT from the onboard 12V leisure battery/EHU 240v-12V supply!
Most modern vans do NEED the onboard 12v supply to power the fridge control circuitry used for all cooling power sources, but the actual cooling on 12v is ONLY when attached to the tow vehicle WITH the engine running! That does of course assume you have a fully and correctly wired pair of the older 7 pin sockets (12N for road lights, 12S for ancillaries), or the modern 13 pin socket.
The fridge draws far too much current (up to 10 amps!) on 12V cooling for anything other than the tow vehicle with engine running to supply, it'd kill the leisure battery in a few hours!