Go to vermontcastings.com. Click on Hearth. Click on Support at the top of the page. Type "rebuild" in the search box. Defiant Rebuild Top to Bottom PDF will appear. This will get you to what you want. For some reason, a more direct link does not. With the damper open and the Defiant in updraft mode, any ash clogging behind the fireback and/or broken/missing secondary burn tube would not cause the fire to die. Make sure the little cast iron tab is fully open over the air intake on the lower loading door side. Make sure the same thing is true of the thermostat flap. These are the air sources with doors closed and damper open. If the fire dies when you close the damper, lots of ash, etc., etc. behind the fireback is the most likely cause, although even this, unless it's really extensive, should not cause the fire to go out completely. Clean chimney with a minimum 8" flue?