Great website. I've been reading some of the Q&A and it's all very informative. My first post is about a Lennox G40 furnace that is 6 yrs old. Dec. '07 the CAI started making a grinding sound as it wound to a stop so I replaced the entire unit including the pressure switch. Worked fine for the rest of the winter but not so this year. I went to put the unit into service a week ago and the CAI would start but no fire. Circuit board LED's pointed to the pressure switch and a meter confirmed that the contacts would not remain closed as required so the sequence would stop. After checking that the flue was clear and insuring that the hose connection at the CAI and the hose itself were clear, I tried again. This time the ignitor heated up but the switch contacts didn't hold so the unit shut down. I jumpered the wires that connect to the switch after the CAI ran for 5 - 10 seconds and the furnace would then run fine. Bad switch right? I replaced the switch and now I have two good switches but no working furnace. I'm heating my house by manually jumpering out the switch each time I need to run the furnace. Any "next step" suggestions? Buy a better furnace? Thanks in advance for the help.