Hi,

I thought I'd share what I found out today as I called an RV store and
told them about my fridge, which does not produce any cooling even though
the 12 V heating element does get nice and hot. 

I asked whether the ammonia solution could be topped off. His answer is 
that, theoretically, it's possible, but it's also VERY expensive and 
costs over a $1000, 2/3 the cost of a new fridge. He added, however, that 
a leak leaves a yellow powdery residue, and unless I find that, a refill 
shouldn't be necessary.

His guess is that there is a clog somewhere in the piping. One way to
remedy that is to turn the fridge upside down (while off) every night for
a period of about 6 days and then test it again, a procedure that was also
suggested to me by Martin from this list. There is no guarantee, however,
that this will unclog it. 

Sami