I have a true blue 90. It is continually running. It will continue to blow cold air. I have looked at the pilot ignition assembly for cracks. Also checked the air flow lines, and the out side exhaust for blockage. The pilots do not ignite.

Not much help to go on. Well, you obviously have a process issue and it could be a lot of things. If it is a 90% heater it doesn't have pilots, it has a spark or flat surface igniter. Lower the thermostat below room temp. Turn off the main power, wait for a few minutes, turn the power back on. Raise the thermostat and call for heat. What happens? We can go from there. Did you look through the peephole? Any codes flashing?

Do you mean the fan is continuously running?