Greetings,

I have a Trane gas-fired furnace installed around the mid 90's. Model# TUE040A924H with a new filter. I'm writing because I am cold. During the day the furnace usually works fine but at night when it gets really cold the furnace will not keep up with the temperature I set at the thermostat. When the furnace kicks on I first hear the Draft Blower fan start, it then ignites, and then the indoor blower turns on pushing luke-warm heat out the vents. A couple minutes later I can start to hear, what I think is, the Draft Blower run sporadically like its cutting in and out. Soon after this starts the air from the vents becomes colder. The Draft Blower continues operating in this manner for a few more minutes and then turns off leaving the indoor blower fan running by itself, pushing air from the vents, for a few more seconds. The furnace then turns itself off completely without satisfying the thermostat. If I then try to restart the furnace by either turning it off and then back on, or, lowering the thermostat completely and then raising it to temperature, the Draft Blower will start up like it should but it will now sound sporadic from the get-go, cutting in and out. It then sounds like something ignites, or tries to, then the indoor blower starts blowing cold air for a few minutes until everything turns off again. I assume the Draft Blower sounding like this is not normal. If so, could something else inside the furnace be causing it to act in this manner, or is it the Draft Blower itself? What causes a Draft Blower to go bad? Could a dirty filter be the blame or just old age? Could the temperature outside affect the Draft Blower? Am I completely off base with this Draft Blower hunch?

It very well could be the draft blower but have you looked to see if the circuit board is flashing or blinking a code that would tell what the fault is? The legend for the fault codes is located on the back side of the blower access door.

I'll check the board and repost any findings.