I have a 12 year old Carrier Weathermaker 8000 two speed furnace.
I noticed the house was cold when I returmed from work, so I looked at the furnace, which was not running. I monitored it for about an hour, but it didn't turn on, despite the fact that the outside temperature was approximately 15 degrees F. I instinctively flipped the power switch to the furnace, and heard a faint hissing, indicating that it was attempting to fire up, It did turn on briefly, but then shut off. The inside temp had dropped to about 60 degrees F, so I attempted to reset the furnace again by flipping the power switch. The second time, the furnace turned on and has been cycling properly since then. What could have triggered this intermittent shut down?