Every few days I have to remove and drain the the rubber tube from the pressure switch to the furnace or it won't ignite. Why is water condensing in that tube? It's not a hard thing to fix-- but I ought not to have to drain that tube at all. Seems to happen more often in colder weather. I'd hate to be out of town for a few days, have the furnace not light and end up with frozen pipes!
My American Standard has a drain trap that has to be flushed every so often or it will fill up the tubing and I can hear that it is affecting the ID fan. You may have a similar problem