Our Georgetown motorhome did the same thing when I turned the furnace on the first time - the AC fans would blow constantly. Turns out we needed to fool with the wall thermostat - set it to cool then AUTO (not high or low fan), then set it to heat. The fans quit running and we just had heat!
Of course thermostats and units vary, and if the manufacturer is telling you this is by design it could be to prevent condensation. But if you have a wall thermostat for heat/cool give that a look.
2014 Georgetown 351DS
5 kids, 2 dogs and an amazing wife!!