Need help with Euroline (MK6 2003) aux 12v wiring

[juventusventus]

Hi everyone,

I have a Transit Euroline MK6 2003 van. It's a gem! Even though I'm quite a hands on/DIY kind of guy I can't seem to figure out how to:

1. Figure out why one of my cabin lights and aux 12v output doesn't work. It's the one all the way in the back of the cabin - see pic. Do you have suggestions where I should start and what I should I test with my voltmeter to find out where the problem comes from. Actually I don't know where exactly that light and aux 12v jack connects to - any tips would be very welcome.

2. By default, I have two batteries. One under the driver seat(main/engine battery) and a second one(leisure) connected trough a relay and located under the co-driver seat. I have noticed that almost all my in car stuff runs from the van's main battery(at least I think since when took out the 2nd bat. everything mentioned still worked) - the radio, 2x12v plugs in the front, the ceiling lights (except the neon ceiling light above the table), the cabin blower fan and who knows what else.
My question is: Is there an easy - or relatively easy - way to switch some or most of these energy consummers on to my 2nd battery - I'm especially interested in wiring the radio(original ford radio) and cabin lights to it.

If you need additional info to be able to help me, I will be glad to go measure any voltages, check any connections, photograph any parts necessary.

[easogs]

What model of batteries do you have ? I have a Euroline MK6 2003 and i am planning to change them.