Sorry to hear you're having a cold morning!  I trust you had enough
bedding to keep warm overnight.  I had to break out the extra
sleeping bag here in the Hayward hills near Oakland, as it got down to 41F.

Karl's last message to this list was January 7.

At 04:56 AM 1/27/2010, you wrote:
>It is possible that my auxiliary battery isn't super charged ...

As suggested earlier, try it with the engine running.  The other
accessories might tolerate low voltage better than the Propex.

The intake might be blocked.  You can inspect both hoses visually
under the van.  (I'm not sure I know which hose on MY van is the
intake!  I'd have to feel for the hot air coming out of the exhaust
hose.)  I wouldn't recommend blowing compressed air into the intake
while it's connected to the heater, as that might blow crud into the
heater itself, making matters worse.  You can disconnect the hoses
from the heater under the van and blow them both out with compressed air.

>If this were a pressure regulator problem, where would I find that
>pressure regulator?

I've never adjusted mine.  Karl did it for me, and it has been
working since.  No point in fiddling with it unless you have a
manometer.  Here's Karl's set-up:

http://mira.sbw.org/photos/20090825/SN851254/
http://mira.sbw.org/photos/20090825/SN851253/

See also the information on Karl's web site.