If you search "aux battery wiring" or some such in the archives,
you'll find lots of info. I just found this which is an alternative to
the infamous "blue wire" (from alternator):

http://gerry.vanagon.com/cgi-bin/wa.exe?A2=ind0908A&L=vanagon&P=R20032

I don't know the '91 but looking in Bentley, if you follow the blue
wire from alternator, (track 6) it runs to 61(path inside fuse box),
then two blue wires exit at B1 one of which splits off and into to
A16, (track 47 in Bentley) then internally (in fuse box again) to C2.
Blue wire then exits at C2. What it terminates to, I don't know, but
it's a starting point I think.

Neil.

On Thu, Apr 19, 2012 at 8:29 AM, Robert Clemmer <n51219@comcast.net> wrote:
> I'm going to install an auxiliary battery under my rear seat in my 91
> Vanagon to power my refrigerator and other appliances without killing the
> service battery. �Any suggestions on where I can tap into for a trigger wire
> that will power the solenoid that will connect the aux. battery to the
> charging circuit only when the engine is running.
>
>
>
> Bob C

-- 
Neil n

65 kb image Myford Ready For Assembly �http://tinyurl.com/64sx4rp

'81 VanaJetta 2.0 "Jaco" �http://tubaneil.googlepages.com/

Vanagon VAG Gas I4/VR Swap Google Group:

http://groups.google.com/group/vanagons-with-vw-inline-4-cylinder-gas-engines