Intertherm gas furnace pressure switch "stuck on close"

[ceci]

Helppppppppp, please. The diagnostic code is blinking 3 tmes so that means the pressure switch is stuck on closed. I tried the following. I first removed the rubber tube from the pressure switch part only and blew lightly through it and the furnce did start and heated up well. Thought I had fixed the problem(was all happy), but the next day noticed it wasn't working again so this time removed the rubber tube completely and put a thin wire through it and no obstruction at all. I then also put the very thin wire into the plastic nipple of the pressure switch(the part where the rubber tubing goes into), but only was able to go in a bit since then hit something "solid" and not sure if I am suppose to try to force the wire through. The bit of wire that went in came out clean. I then also put the wire through a metal nipple where the other end of the rubber tube contacts to(I think it is part of the draft inducer). That wire also only went in the length of the metal nipple and not any further since I again hit something "solid" and wasn't sure if I am suppose to try to force it through. Again, the length of the wire that went in came out clean. The furnace didn't start, but then much later noticed heat and worked for a while since the house got hot, hot, but then again stopped working. I hope I was clear in what I just wrote. I tried.

Thanks for any help that can be provided,
Ceci

[surenuff]

That switch is a negative pressure switch. It is normally closed. Plugged exhaust would cause it to stay closed. Could just be a sticking switch.