Furnace on while driving

Also, to keep heat in the cab area while driving, you can install a curtain on a shower curtain rod just behind the seats so heat stays up front from engine heater. Insulation over windows is best, as that's where the heat loss occurs. Home Depot and Lowes sells it on a big roll that you can cut out specific sized window covers. If you worry about freezing water lines as a reason for heating the entire unit, while driving, you can winterize and use bottled water kept near front engine heated area, and use it for washing, then add non toxic antifreeze down the drain so grey and black tanks do not freeze.