I'm confused about the functionality of the isolator switch fitted to my van (2008 Newlands Concept).
It has two positions: CAR and POWER (it looks to be a household wall switch)
![Isolation Switch](https://cdn.exploroz.com/images/forum/uploads/192050_0__TN600F.jpg?gid=205828)
Isolation Switch
I assume it should function thus:
1. In POWER, everything in the van can receive 12VDC from the house battery EXCEPT for the fridge 'motor'. The fridge light and the gas igniter still get 12VDC, as do all lights, pumps and sockets in the van.
This prevents the fridge drawing high-current power from the house battery when you are parked if you forget to switch over to gas or 240V.
I've checked the operation, and it all works as expected.
2. In CAR, everything should be isolated from 12V, EXCEPT the fridge which will now only operate on 12VDC. This prevents water pumps/lights etc operating while you are underway, and the high current-draw fridge 'motor' is now fed by the vehicle alternator (not the house battery).
On my vehicle I have the power wire at the trailer plug connected to my vehicle auxiliary battery, so power is available to that circuit on the van at all times the trailer plug is connected, not just when the alternator is operating. I also have a separate anderson connection which feeds the van house battery directly.
My problem, is that in CAR, everything isolates as expected, until I plug the van to the vehicle, then I get 12V to everything in the van, including to the fridge 'motor'. So I'm losing the isolation feature. I get the same issue with the anderson connected or disconnected (I thought it may be feeding stray current somehow).
I assume there must be a large relay somewhere in the system that connects the house battery to the van with POWER selected, but I can't find it anywhere. Might it be located behind the fridge? I can hear clicking but think this might actually be the fridge switching over.
Any ideas? Anyone have knowledge of this type of circuit, or a basic diagram? I have some limited electrical knowledge but my probing with a meter has yielded little results. With most of the wiring sandwiched inside the van walls it's hard to trace the wires.
Or, is the switch really just a fridge changeover switch and not really an isolation switch?