In addition, others on the list have pointed out that the VW
alternators/regulators don't cope well with the additional voltage drop
that the diode-type isolators (the ones with fins) provide, so with those
isolators, you may end up not having either battery completely charged.
When I put in my Optima, I just replaced the original relay (30 amp) with a
50 amp headlight relay.   Works perfectly, but I think the original relay
should work fine also, since I put a 30 amp fuse in the secondary charging
circuit when I added the Optima and it has never blown, even when charging
the Optima from dead discharged state.

Dave
Lincoln MA.
87 Wolfsburg
90 Westfalia

At 08:29 AM 10/30/97 -0500, Lawrence Johnson wrote:
>Steve,
>A relay from a set of driving lights rated at 40 amps is sufficient for
this job
>(under $15). An isolator is not necessary and wastes energy (hence the
cooling
>fins). To be on the safe side, add your own wire (6 gauge) for the charging
>circuit. Leave the existing fridge wire and relay because you do not want to
>discharge either battery with the power hungry fridge. Change over all the
rest of
>the camping wires to the aux battery (fusing each of course). An easy way
to put
>the cabin lights and radio and cig lighter on to the aux battery is to
remove fuse
>number 3 and run a wire from the aux battery to the fuse connector.
>Larry
>'86 Syncro Westfalia
>~~~~~~~~~~~~~~~~~
>Steven X. Schwenk wrote:
>