Gas Heater comes on when Elec Heat is used 2008 Fleetwood Excursion 40'

I know my heat pump will only work by itself (no propane furnace) when there is a less than 5 degree difference between the stated temperature reading and what you want the temperature to be. 

Lets say the thermostat reading is 65 and you want it 75 the propane furnace will come on untill temp reaches 70 or so. Also as said the heat pump will not work if temp is below certain degree.