York Stellar Plus flame won't say lit for more than a second
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!
Your problem is most likely a sensor or detector closing the gas valve. The diaphragm must have a vacum at all times, the flame sensor must be clean and seeing a flame, the flue must be clear and open from the furnace to the outside (we have had several cases of birds, their nests and wasp nests blocking vents), and the heat exchanger should be checked for rust-out especially along the bottom.
The burners may need to be taken out, wire brushed, make sure all holes are open (shine a light in the end and be sure you can see it through each hole). In the case of a cross-over pilot tube, make sure it is clean with no spiders and webs inside it.
Thanks for the suggestions, I'll, go through the list and see if I can find anything out of order.
Yesterday I did remove the flame sensor and inspect it; it looked alright, a very slight amount of surface rust in one small spot and a somewhat dull finish, but not sooty or covered in anything at all. Nevertheless I did take some sandpaper to it and shined it up, and when I put it back in the flame lit right up and stayed so. The flame-out problem is intermittent, though, so it could just be coincidence. I'll have to do more testing to figure it out.
Once I can get consistent flame, my next order of business will be that the fan for the ducting does not turn on when the furnace does.
Judging from what you are saying that the flame goes out a few seconds after it is lit, I would look more closely at the flame sensor, also you want to make sure you 3.5" of W.C. at the output of the Gas valve. I've come across this too many times that someone has adjusted the gas pressure down on the gas valve to reduce the temperature rise of the furnace due to incorrect duct/furnace sizing. If the flame is on until the blower motor starts to operate then I would lean towards a cracked heat exchanger.
Your problem is the flame sensor, the long sensor that you used sandpaper on is the flame sensor and you should lightly clean with scotch brite or sandpaper each fall before winter. This senses the flame during ignition and keeps the gas valve on.
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