The furnace is going into what is called a "lock out" condition. It is a saftey built into the ignition board that if the flame sensor does not see the flame it will shut down the gas valve. The older style(prior to 2002) furnaces let the fan continue to run with no heat; the new ones have changed the design so the fan will shut down too. There are a couple of reasons yours is doing what it is. 1 the board is bad; 2 the furnace is cycleing on high limit and the board tries to ignite while the high limit t'stat is open and goes into lock out. 3 the burner may be partially blocked or a flake of rust is covering some burner holes. 4 you have an obstruction in the outside air/combustion circuit. If it is cycling on high limit make sure no vents are blocked or ducts kinked. The return air is important too; keep it clear of blockage. If someone in your area can check the DSI (direct spark ignition) board to verify that it is good or not may help you diagnose the porblem. Good luck and keep us posted.
Mike, RVIA & RVSA Certified Master RV Technician
Amy, Dr. Assistant - Roxie & Mei Ling, four legs each
2000 Gulf Stream Scenic Cruiser 450 hp & 1330# torque
06 Saturn Vue, 06 Chevy Z71 4x4 & 2014 Corvette Z51 M7