In my case the furnace needs all the piping it has to exhaust enough heat
to cool the furnace to a point where the high temp switch will not shut off
the furnace.. If that happens, the blower runs continuously and kills the
battery, and you have to shut off the furnace , wait 10-15 min and then you
can turn on the furnace again...
The previous owner had fixed the problem by adding an extra duct in the
kitchen, but used an adjustable outlet that could be shut off .... and of
course it got shut off.... the switch had apparently operated too many
times (even though I had replaced the furnace) and the relight process
failed.... I had some nice conversations with RV shops that were warranty
repair places for the furnace and they were not interested on doing
warranty repair on trailers they did not sell... not that they were
refusing (this is where the blood pressure goes up), just that they did not
have any openings on their schedules... even if I towed it right to their
door...
The point is that you might not get the outcome you desire by capping any
of the furnace outlets... and it won't fail while you are at home... it
will fail come cold night when the furnace is running almost full time
trying to keep the temp in the trailer comfortable..Your first clue will be
waking up in the cold , but the furnace is running... like you ran out of
LP... stove works so there is gas... one of the overloads in the furnace
killed it and the relight process may or may not work... if it does not,
forget the furnace and go to an alternate plan to keep warm....
Jim