My problem started last year. I too have a Trane XB80. I walked through the steps of turning off the switch and gas. I waited for the smell of gas. When there was none, I proceeded to turn them back on. The blower would start but the igniter would not. The lights signaled that the pressure switch needed to be replaced. We found the information from the switch, ordered a new one and replaced it. A couple of days ago, the heater started doing the same thing. Last night and this morning, we have walked through the steps several time. Is it possible that the pressure switch continues to go out that fast once it goes bad the first time?

The pressure switch is a safety to let you know if you have a restriction in your flue pipe or if the inducer motor is not moving exhaust or a hole in heat exchanger. All of the above are serious scenarios and could be a deadly problem. Pressure switches hardly ever go bad.