Thanks for the help.  It looks like it is preferable to wire the fans in
parallel, I'll have to remove the frig and do some rewiring in the near
future.
For those who asked, I used Friddgemate brand fan model number A10-2710.  I
think I got it at Camping World.  For installation guidance I used the data
in Bill Davidson's original post back on 8/18/98, Fw: Dometic.  Bill
reposted on Monday 4/26/99 at 8:55, Re: Dometic Improvements Adding Fan.
Blake Heinlein also has a great web page regarding the Dometic,
http://www.ecst.csuchico.edu/~bhein/fridge/fridge.htm .  He has a picture
of the back of the frig.  If you want to add an extra fan in parallel, the
new fan wires could be spliced into the existing blue and yellow wires
shown in picture http://www.ecst.csuchico.edu/%7Ebhein/fridge/2back.jpg .
Directions to remove the frig are in Bentley and in a post from IR Student
on 6/17/98, Re: VW Camper Refrig repair.
I was going to do a series vs. parallel write-up, but I think pictures are
worth a thousand words. See Bulley's picture from earlier today, it is
excellent and should help explain the difference between series and
parallel; www.bulley-hewlett.com/Ser&Par.html

Since we are talking series and parallel wiring circuits, how should the
trigger wires to the relays under the driver seat be wired?  I plan to add
a Dual Battery Relay under the driver seat to isolate the Optima and I want
to use the trigger wire signal from the existing refrigerator relay.  My
original plan was to wire the trigger side of the relays in series, but now
after this discussion I believe the best would be to wire the trigger side
of the relays in parallel.  What is best?

Kevin M.
'89 Westy
Bothell, WA