Furnace blowing cold.

Since this is an older unit, I would agree with checking the "sail" switch. The "sail" switch is a metal flapper on an arm. Basically, when you first start the furnace, the fan starts up to clear the unit of any gas. Once the fan gets moving, the air flow forces the "sail" switch to move. Once it moves, it turns on the gas and allows the unit to ignite. Sometimes, these switches get stuck. Often you can look inside and see the flapper and check to see if it's moving.

Don't circumvent the "sail" switch.

In rigs that old I doubt there are lights/diagnostic devices.

If it were me I would check sail switch - then the heat limit switch - and see if any propane obstruction to furnace. If that all checked out I would have board tested.

Do you have any registers covered or otherwise closed off?

There is also a sail switch in the furnace that proves you have proper air flow. Sometimes they stick.

Ok, if the over limit switch trips or the furnace fails to light it is SUPPOSED to shut down so long as you have the OEM board. not sure that Dino Boards do that.

Now I knwo Atwood best. on Atwood if you open the outside access there is a switch (Actually a circuit breaker) on top of the blower housing. Turn it OFF, then set the Thermostat high enough so it will call for HEAT when it can.

Turn the switch on and observe the operation

Normal operation
Fan/Blower starts
Then you may hear the CLICK of the gas solenid and the Snap, Snap of the ignightor
Then it should FLAME ON and continue to produce heat.

Optional it may flame off, then re-start 2 more times then if you look at the control board you will see a flashing LED (post pattern).

IF you see that flashing led.. Post pattern.. IE 3 3 3 3 3

You should be able to remove the cover out side. Take a look at the circuit board and you will see a red light blinking. It may be different combinations. Then there should be a list right there or in your manual to tell you what's wrong.

Sounds like maybe the front furnace tripped the over temp. sensor that, for obvious reasons kills the supply of gas at the furnaces valve.

If that’s the case just shutting it of at the thermostat waiting a moment then turning it back on should do the trick.

There are other possible causes, such as the sail switch, but generally if the furnace was running previously it’s not likely to be the culprit.