In August our front furnce would not lite and we found critter nests in the exit port. After cleaning the exit out, it still would not lite and so we broke out the little portable electric heater for the front and ran the back furnace.
Our propane monitor indicated that the tank was full.
When we got home, we took the furnace out a few times and eventually decided that we would try to replace it. Well, it turns out that these furnaces aren't made any longer so we said we'll look around during the winter and try to find a suitable replacement.
Meanwhile, I read somewhere (either here or in the Airstream manual) that the front furnace will not actuate heating when the propane is too low - in order to keep the occupants sleeping in the rear warm while sleeping.
So we talked it over and noted that we had acutally ran the propane quite a bit during the cool spring trip to the beach and our 5500 camping trip this summer and the 7 rallies we had been to and that a 3/4 full reading might be an incorrect indication of the propane level.
We decided to fill the propane just before putting the baby up for the winter last weekend. When we returned, my husband decide to "give it a shot and low and behold it worked! Yippee!!! The manual was right!!!