#1 You gotta find the model # for me. Me helping you is like the blind helping the deaf without that #. This is going to get a little more technical that I expected. Im glad you looked at everything I wrote down. Im going to guess and say that the "pressure switch" is your induce draft motor vacuum switch, is it a round disc with a hose attached to it? make sure there is no corrosion inside the tube going to the vacuum switch and inside the switch itself. If you get a little chunk of something it will jam it up. Hunch #2 I'm going to take a wild guess and say you have a 90+ furnace (90% or better efficiency). Does the furnace have any 1.5" - 2" PVC tubes coming out of it? This is only a guess but I bet at night when the outside temperature is low and the humidity is up the induce draft motor is struggling to keep the vacuum switch closed because the air is so dense with moisture. If i am correct your system pulls air into your burner compartment with the "induce draft motor" and pushes it out of the house a similar way that it came in. Now as a safety measure Trane installed a vacuum switch on your suction side of the induce draft motor. this will kick the furnace off if the induce draft motor fails. is quite common. If you dont have 2 pvc pipes coming from your furnace, you need to look at the seal around your induce draft motor, its RED RTV silicone same stuff that you can but at the auto parts store. Also look at the vent for the furnace. If there are too many tight bends its going to be hard for the inducer motor to push the air out. If you can find your owners manual and the install instruction it will explain how many bends within so many feet your system is allowed to have.