For the 12v.
Under the sink you will see a connector with two wires going in and out each end.
Put a volt meter across the two wire and you will see if you have 12v going to the fridge,remember it will only work when the engine is running as there's a relay under the drivers seat which makes sure it doesn't drain the battery.
Hmmnnn.... under the sink there is a set of wires that do join with a conector... but that goes through the floor? I followed them and they go down to the gas cylinder under the van and I think they are for heating up the gas regulator? There is also another switch with wires under the sink, but that is an aftermarket job and appears to make 'live' a couple of wires under the rock n roll bed... I think they were for an after market water pump... so, no sign of any other fridge wires...