Drum turns.
Igniter glows about 15 seconds, valve clicks, flame comes on 5 or 10 minutes
Then flame goes out and will not re-ignite.
After about 1 minute igniter glows about 15 seconds, valve clicks, no flame.
Outlet air is cool but the glow-click-no flame cycle repeates each minute.
The air ducts appear clean (right now it exhausts to open air).
The flame sensor is continuous (when cold).
3 thermostats checked within specification.
3 coils checked and are not open.
Any help would be appreciated.