We have a medium-size popup camper. 2015 Forest River Flagstaff MAC. The heater has been acting up lately. Very inconsistent. Seems like whenever it is running off battery power, the fan will click on when I turn up the thermostat, but then it clicks off after about 30 seconds. The propane flow never kicks in. I probably tried it 25 times. No luck. However, when I use shore power and turn up the thermostat, the propane usually flows on the first or second try. Our battery is not old. I even had it tested at Wal-Mart a few weeks ago and it has plenty of life left, and I also bought an upgraded charger to seal the deal (so I thought). Any thoughts would be very much appreciated.