My furnace is only 4 yrs old, believe it is high efficiency. This morning it was not working properly. It would start on and right before the flame fired it would shut down. The code was pressure switch open inducer on. I saw that "mygirlsdad77' mentioned there needs to be water in the drain trap so it creates a vacuum. My little clear line going from the vent to the drain had condensation in it so I shook it loose and there is now a little bit of water in the bottom of the line and the furnace is staying on... Is there anything I can do to prevent it from turning off again?