If you are running the propane heater under the trailer when the belly is still covered guess what? The propane heater is doing next to nothing but warming the coroplastic skin of the underbelly.
Valves are frozen/waste water is frozen at the valves.
I'm guessing you did not heat the valves/tanks/waste tubes electrically?
If you've been relying on the furnace to get heat into the under belly you're going to have to spend some time with it running to get some heat down there.
Even if the remote dump valve cables are bust you're still going to have to get down into the area and open it up to get to them.
