OT: RV furnace help needed

 During Christmas, my wife and I moved into our toyhauler so all our
guests could have their own rooms...the night time temps got down near
30°F or so, and the second night the furnace refused to light. It
would go through the usual cycle--

*blower on
*about 30 seconds later, the ignitor would start clicking then stop
*about 15 seconds later, ignitor action again, then stop
*about 15 seconds later, ignitor action again, then stop
*red LED starts flashing on controller board indicating ignition fault
*about 20 seconds later, blower off

Turn thermostat switch off, back on, repeat above, etc.

The next day I went out to figure out the problem, except that it
fired up on first try. Dang.

That night it wouldn't fire up when it got cold again.

I got out my garage heat gun (wife's old blow dryer) and heated up the
furnace, and sure enough, it fired up on first try after warming up
the sensors and controller.

Any idea what the problem is?

It could be a bad sensor, a bad controller, or maybe these things are
just designed with such a high setting for sensing the ignitor is on
they simply won't function right in temps below 40°F?

Anyone have trouble with their RV furnace in cold temps?

--
Charles
'99 YZ250

 Charles,
Somewhere on your furnace you have a gas valve. That is the thingy
with the main gas pipe going into it. It also has a bunch of wires
going into it. When the sail switch and the thermo switch. Put a long
screwdriver up to the gas valve and place your ear on the end of the
screwdriver. Turn the switch on again and listen for the valve to
open. If it doesn't open then you might have a problem with the sail
switch. You might have a bunch of dust bunnies keeping the sail switch
from working properly. I doubt if it is a gas valve but you never
know. OF

 Do you know how the sail switch works?

 Charles,
The sail switch is nothing more than a micro switch with a long piece
of material that extends into the air flow. The force of air from the
blower trips the switch and thus allows electricity to continue forth
and open the gas valve (I previously spoke about) alowing propane to
enter into the furnace chamber where your electronic igniter lights it
creating heat. If the sail switch is not thrown it tells the gas valve
not to ignite because the air blower is not working and the system is
going to overheat. It is a safety mechanism. Mine recently would not
trip and I had to remove the furnace and clean all the lint and cat
hair from around the switch so as to allow the gas valve to open. This
is a common problem. To access the sail switch you must remove the
furnace. Mark all your wires first.OF

 OK Charles. Fire up the Multi Meter and poke around. My unit has a
pilot light and is considerably different. Double check the circut and
see if the sail switch is autonomous. Hook your meter up to that
circut and see if it works when the blower is on. Let me know how
everything checks out. I am curious. OF