electrics problem - caravan or car?

Maxey

We have a bailey unicorn valencia and used to have a peugeot 407 estate. When we hooked up to go on holiday the electrics blew and everything failed on the caravan.  We now have a Hyundai Tucson and have been away 3 times but most recent the fuse blew in
the car and everything stopped working again.  Has anyone experienced this before? The caravan dealer insisted it is not the caravan. 

Where does the wiring from the tow bar connect to the car fuse box. We have a black and red wire stuck into a 13 amp mini fuse. Is this correct?