The relays in the engine compartment, which distribute the 12 voltage to the Caravan section, and to the fridge when travelling. They are located close to the engine starter battery.

The red arrow points to the fuse which protects the cables and current to the caravan interior. On my assembly there was another 5Amp fuse which was not connected to any wiring!
The ribbed cable at the top of the picture goes to the impact reset button. 

I found on my own Motorhome that the female contacts which secure the cables inside the relay holders where being pushed out by the relays them selves. This in turn meant there was no charge current going to the leisure battery. Another point to check. The cure, hold the relay then push the cable at the base of the relay bracket. This will push the female contacts onto the relay spades.

In Mar. 2012 I removed this assembly and introduced new one.