At 12:42 PM 6/1/2012, Jon Durham wrote:
>The Dometic frig in my 85 Vanagon runs great with gas or AC current but
>will not cool much with battery current. Why?

Jon, the AC and DC heaters are each rated 85 watts; but because of
the lower voltage and correspondingly higher current the DC one is
very subject to problems with connections.  Go through the whole
system (including the top of the fridge, if necessary) with the
fridge running on DC and measure the voltage drops in millivolts
across each connection, and between the connection and the wire an
inch away on each side (use a needle).  Anything more than a few
millivolts (less than five, say) is a reason to clean up the
connection or re-make the crimp connector onto wire that's been
carefully scraped shiny-clean.  The fuse itself will necessarily have
a little drop across it, that's how it works.  But between the end of
the fuse and the terminal should be practically nothing.  If
the  fridge fuse isn't already that kind, buy some of the
glass-enclosed ones from Littelfuse that mimic the European
type.  They are much less prone to corrosion than the
others.  Remember that the actual contact point on the fuse holder is
the edge of the little hole in each springy contact.

It's possible for there to be problems with the heater itself, but
much less likely.  One thing to check, though, would be that it's
properly inserted and secured in its tube attached to the boiler.

Yours,
David