Had this problem last spring with my 2009 JF 24rks.
blower comes on for a couple minutes, ignition fires(you can hear it click/cycle 3x) furnace lights for a couple minutes and produces heat then it shuts down. You shut t-stat off and reduce temp all the way, wait a few minutes and does the same thing over and over. Sound familiar?
What I did to repair:
Obtained any service info from atwood. Found board indicator light flashing, didn't believe it was bad or any other component was bad when checked out to service manual parameters. Was ready to pull furnace untill I found out that I would have to pull kitchen sink out to remove furnace to be able to work on it. Took trailer to CW for repairs, estimate $600+. They said board and sail switch need replacement. Do to time constraints when repairs were promised, I picked up trailer and decided to go for it myself, after paying diagnostic fee. Bought board and sail switch on line, pulled furnace and replaced those items. Lo and behold, that wasn't the problem. Since I bought those items they were mine( no return on electrical items!). I also checked out the LP pressure at the tanks with a self constructed U-tube manometer plumbed into the system to verify the specified 11" LP water column gas pressure.
My next move was to replace the igniter which was no easy chore since you literally have to break the furnace in half to gain access to it. This is a major pain in the butt! The old igniter looked good, sparked ok, BUT this component sends a voltage feed back signal to the board and tells the board there is a flame present and inturn the board signals the gas valve to remain open. After 6-7 time of R&R of furnace, it works! But it did cost me $600 by the time I got done fooling around with it
Have fun! Hope this give you some insight