Aux\Veh switch not working

[Touchwood]

I've suspected for some time that the switch on the internal control panel which is supposed to allow use of the vehicle battery for internal 12v. electrics isn't working, but never had occasion to use it "in anger" as it were. As I posted some time ago my habitation battery has died (not replaced it yet) and when I checked today it's completely flat. This gave me the opportunity to check out my suspicions re. the switch, and it doesn't seem to be working - plenty of juice in the vehicle battery but the internal lights refuse to work with the switch over to veh. I have a circuit diagram in the handbook but despite having been able in the past to work my way through circuit diagrams I can't make head nor tail of it - can't even see the veh battery on there.

Any ideas on what may be wrong? Is it the sort of problem an amateur is likely to able able to fix, or should I resort to an expert?

 

[pappajohn]

It may have the switch but is it wired for hab and cab ?

Take out the switch and see how many wires are going to it.

None cab wired should have two wires...one to the centre terminal (common from charger) and one to an end terminal.(to hab battery)
cab wired should have one centre and one at EACH end.( hab and cab)