Atwood Hydroflame Furnace Issue

Our 2005 Okanagan Truck Camper has an Atwood forced air furnace. When it comes on, it works well -- warms the camper up quickly. The problem is, it will only come on if the furnace itself is cold.

At first, I thought it was the wall mounted thermostat. So removed it, and experimented by turning on the cold furnace by clipping the two wires together (the ones that attach to the back of the thermostat) -- thus closing the circuit. The furnace came on normally, and I let it run for about 5 minutes; then unclipped the thermostat wires, opening the circuit, and the furnace shut down normally.

Then about 20 minutes later, tried clipping the thermostat wires together again, and the furnace would not come on -- no reaction whatsoever -- no fan, no clicking -- nothing. It was over an hour, before it would once again start up, suggesting an issue with the furnace's internal temperature?

There must be an adjustment for this -- an internal thermostat of some kind (that prevents a too-hot furnace from running)?

It'll likely have to be fixed by an RV shop, but I'd like to know a bit about it, so I can explain to the tech exactly what the problem is.

Any advice will be greatly appreciated...

Thanks
Steve