I just installed a second battery under the drivers seat. I took out the
existing relay and use a surepower 1315. I disconnected the two other little
wires at the old relay, not really knowing what they are for, and used the
thickj red existing wire, which is always hot, to connect to the main
battery side of the surepower. the other side of the surepower is connected
to the aux battery.
the aux battery directly feeds the wire to the fridge that goes through the
b pillar fuse box and a new cable that i ran to the main fusebox which now
directly feeds the cables from connector points b11 and b12. according to
bentley, that should be radio, interior lighting, cigarette plug, that are
now going off the aux battery.
however, theory and actually observed behaviour dont quite match.
(background, this is an 87 full camper, subaru ej22 conversion, headlight
relay upgrade, otherwise stock wiring)

so with b11 and b12 rerouted and all the connections for the 2nd battery
made, but not yet installed and hooked up, the following weirdness is
observed:
-the fuel gauge is not working.
-the hand brake warning light is stuck on on
-the cabin lights and back camper light still work (which they shouldnt with
b11 and b12 without power.

if i connect the second battery, with ignition off:
-the fuel gauge comes on
-hand brake light is still stuck
-water temp sensor starts blinking for a little while, but then goes off.

if i know switch on ignition:
-the fuel gauge goes off
-the hand brake light is still stuck in on

what the ?????
i can only think that b11 and b12 are routed differently in my van, but its
a miracle to me why the fuel gauge goes off again when ignition goes on.

florian