Came across this forum looking for help with my malfunctioning furnace and after looking through and not finding a similar problem to mine, I thought I'd register and post.
I have a York Stellar Plus, No. P2UDD10N05701C; not sure how old, house was bought a few years ago and the furnace was already here. Here's what's going on. If I turn the furnace on via the thermostat, the blower starts and I can see the glow plug light up for several seconds. I hear a click and the gas ignites but only for a second; it's as though it's getting blown out. The cycle repeats several times, and then eventually the furnace just gives up...the blower will still blow for as long as the thermostat is on.
The other problem I've noticed is that when the flame does stay lit, the fan for the duct systems won't switch on. If I turn the fan to on instead of auto, it'll turn right on and if I switch it back to auto, it usually just works as it should. Why it won't start on its own is the other problem I'm trying to work out.
I don't have much experience working with HVAC systems, but I'm definitely mechanically minded and so I start tearing into the unit, seeing if I can figure out if something is malfunctioning. I noticed was that the Condensate Pan Lower Tap switch was leaking; the diaphragm wasn't holding the vacuum. I found where the leak was and patched it and now it's holding vacuum. For a few days the heater worked just fine, but now it's back to doing the flame-blow-out routine.
At this point I'm not really sure where to go next; I've looked at the schematics and done some voltage and continuity probing and nothing has come back out of order, so far as I can figure. Again, I'm not very experienced with HVAC so I'm not really even sure what I'm looking for. If anyone can help out, I'd be much appreciative!