I'll be heading out there this weekend and will try the external power supply. As for the limit switch, I think I will change it as a part of preventative maintenance, but it is switching at the time it is designed to (170F). If the switch didn't trip when it does, it would allow the heat exchanger temp to continue to rise and get hotter than designed and could potentially crack the heat exchanger. Part of me would be interested in jumping the switch out just to see how hot it would get without the limit switch, as it was still rising pretty quick when the switch cut the gas, but I don't want to risk wrecking it.
Something occurred to me last night... The previous owners definitely wintered and lived in our trailer, there was evidence everywhere. I have to wonder if they ran compressed natural gas instead of propane. One of the stove burners runs super hot with a high flame (more than I've seen on any stove in a home or RV), to the point that you need to run it at medium to keep from catching the stove on fire with a pot on top and our water heater is much louder than others that are comparable.
What if the previous owners got the orifices modified to run on CNG? The holes would be enlarged and would provide a much bigger flame if used with propane. I'm not sure how I could verify that though. Would there be any other telltales of gas conversion (different tank connection, different regulator at the tanks, etc...)? I may be wrong, but it could also be an interesting explanation for all of it. Worst case I may have to call the dealership I bought it from and see if they can contact the previous owners and ask them. I'd like to at least rule it out. The furnace has acted this way since we bought it last season.
1999 Spinnaker 36RLE...