Thanks for responding. I guess I don't know for sure the pressure switch is bad. I'm taking the Lennox's tech word for it. When he was there, he tapped on it and got it to work and it's been working flawlessly for a couple days since he was there. I just thought I would go ahead and get the part in ahead of time in case it (or whatever) decides to act up again. I thought about taking the hose off to see if it had debris in it or was cracked, but again was waiting til it malfunctioned again. As far as the new pressure switch physically fitting, I don't forsee that as a problem as the pictures I've seen show it to be identical in every way. I may take your advice and take the switch locally and see if they can match it up to a proper 0.30 WC model. I was just so confused that the exact same switch model number being offerred today has a different WC rating.