Hi Jeff.  The fridge uses a cooling fan that is thermostatically 
controlled.  It comes on when the ambient temperature is around 20 
celcius or up.  Sometimes it will run for hours in hot weather.  This 
works when the fridge is any mode...(gas/12volt/110volt).  I have 
been camped for days without starting the engine, and have never had 
a problem with battery drain.  If you put your hand by the vent that 
is beside the table, you can feel the warm air coming out, and next 
to the window.  That little fan is very efficient at ciruculating 
air, with minimal electrical consumption.

I also have an alarm system (a Clifford).  This unit is in standby 
mode when disarmed and continually draws current from the battery as 
well.  No problems with battery drain either.

Hope this helps.
Harry.
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Harry Yates      Internet: hyates@bcit.bc.ca  Burnaby, BC
'90 Syncro Westfalia
'87 Golf Diesel