Westfalia Instructions Please!

I'm new in town, but a long dedicated T3 owner. My first bus is a 1980, Westfalia with a 2.0ltr. Air-cooled Engine. She is going strong. 

Yesterday, I became the proud owner of a 1990 California T3. Immaculate & totally original Westfalia. It's all modern, grey & shinny inside, quite a different experience from my 1980, although principally they are identical. 

The California came with a VW instruction manual, but nothing about the Westfalia bit. I'm already scratching my head..... here's a couple of questions for sure all of you will know, but for me, it's rocket science this-morning. 

Firstly, The Van has two batteries. One under the drivers seat (LHD) which (like my other T3) is the Caravan battery, and then one under the passenger seat which is the engine battery. There are no external switches, volt meters or anything else. From the start, I notice that all the interior lights work off the Engine Battery!, so I wonder what the Caravan Battery is actually doing?..

On the cooker front is a set of LED lamps and two micro switches. 

One Switch seems to have something to do with which battery the LED's are reading (I think), the other switch switches off the LED display accept for one red LED....  Any ideas? 

Does anyone have a standard Westfalia wiring diagram? 

Still in the same area, Behind the drivers seat on the bulkhead of the Sink,  is a bank of 4 fuses. I screwed them all out, but nothing happened. Are you 12V or 240v?

From what I can see, the fridge, cooker unit & bedding area seem almost untouched. The LPG Tank that feeds the fridge & cooker is 95% empty & I get the impression that these have not been used for many years. Is there a service sheet for servicing the Electrolux Fridge?.. I imagine it is full of dust!... The 12v & 240V of the fridge I am told works & as said, it all looks brand new, save the dust!... Tips, ideas? 

Lastly, on this 1990 model VW, is there an automatic system to switch over batteries, or dual charge them?, I'd appreciate if someone knows how the system works (in standard format)

That's a lot I know......, but would be very grateful indeed. I've a good technical head, a head for wiring & general engineering, but just want to know a bit before I start delving into sorting this all out.

Thanks a million in advance. 

Seen this?

This looks a good replacement....

or this is what was used on the thread above

I was going to do mine but BBB is still good so going to stay as I am for the mo.

Sorted!......... 

MH..... 

I'm going to run Separate Voltmeters for both batteries & two main switches so batteries can be isolated complete or simply switched off. I only need a 2amp permanent feed for the radio memory & clock, so that I will run off the motor battery. On the standard charging system (from the 90amp alternator), I suppose the charge runs through a diode, thus avoiding 'connecting' the batteries?.. I know there are various solutions to this, one which is fitted to my Old VW, which is a big Diode block mounted in the engine bay, directly to the side of the Alternator. One wire in from the Alternator, and two wires out, A, for the Motor Battery & B for the leisure battery.... YOu familiar with this?, or does VW build this in on the later models such as mine...... Thanks again...... 

Is the BBB available to buy new? or good second hand?..