[{tpc}]

One of my "initial" un-winterizing techniques it to find the furthest spot away from the propane tanks and get propane to it first. For instance, the quick connect for the gas grill is located at the back of a lot of trailers (though not all). In this case, I have found that by opening that valve and getting the gas grill to light would help to push "air" out if the system for other things that could also be "T'd" off of said line.

I'm sure it doesn't work in every case, but in my case it has. Saved me a lot of fret and worrying about bad boards and regulators. Maybe something to consider.