Avoiding freeze-ups while towing in very cold weather?

If the vents are clear you can run the furnace in transit.

www.ultraheat.com Combo pads work on 12v or 120v. Install is easier before the cover goes on.

My thread on circulating hot water.
Newest update: Connected a relay so when the furnace cycles on so does the pump. Manual switch also if desired.

For a real expedition I would also carry a third propane cylinder.