York furnace: ignitor..click..but no gas?
I live in Chicago, 10 year old townhouse, with the original York gas furnace. I added a LUx thermostat a couple years ago. The furnace had a board replaced a couple winters ago. Within the last week, I've noticed that air temp was below the thermostat setting, and that the exhaust fan was droning on continuously. I took the the cover off the furnace and stared at for a while. I'm finding that after a heat cycle, the gas will click off, with both blowers continuing to run. After a few minutes, the ignitor glows, then I hear a click, and sometimes the gas kicks on, sometimes it doesn't. When it doesn't the main blower goes off after a while, leaving the exhaust fan running continuously. When I drop the temp down on the thermostat, the exhaust fan goes off. When I bring the temp back up, the furnace will sometimes kick on, but again, sometimes everything goes off, but I get a click with no gas... Is this a fan limit issue? DIY repairable? Also, what are the normal settings for the fan limit controller? My unit looks similar to the one here... http://toad.net/~jsmeenen/blower.html Any help would be greatly appreciated.. Jim Did you check to make sure all the wires are ok, and in it's place? Do you have a meter to check for power at the gas valve? Hi Jay, I checked the connections, and they look okay. I'll have to test the gas valve tonite... Jim The first thing you want to do is to make sure the thermostat is not the cause of the short cycling. If the anticipator is set below .4, for example. or, if heat is gettin to the thermosat and causing it to shut off and on too often, which overlaps with the cycle going on in the furnace. You have to see if your thermostat is a cause of your problem. And I don't mean a malfuncion of the stat istself, but rather fro those two things I mentioned. The quickest way to rule out the stat is just to crank er up to 80 and go back down and watch the furnace and listen, again. THEN let us know, after you do this. EC, The heat app. has nothing to do with the gas not fireing up in the burners.. I feel that he has a bad gas valve. but I want to make sure he is getting power to the valve. Another thing to check is the flame sensor. It may be located on the far left side of the burner compartment. It's a small metal rod that extends into the flame about 3 - 4 inches. Clean it off with a dollar bill or scotch bright and give it another try. Otherwise you're gonna need a meter to check other things and if this baby has not been cleaned and serviced in a couple years it would be a good time to get it done. It's not the limit. The key in your post is when you said SOMETIMES the gas clicks on and sometimes it don't. With a flame sensor problem ONLY, you will get the flame, alright, ALWAYS - but THEN the flame wil go out in about 3-4 seconds usually. You could have a 'not completely burned up' hot surface ignitor. These things have to glow REAL bright and not have any additional resistance occuring in them, for the gas to be ignited off the glow. I've had to replace ignitors for the very symptoms you listed. I didn't know back then, until I ran this by a furnace guy I know who told me this. I put in a new ignitor and no more problem. You can test the resistance on these but I can't tell you what the figure should be, off hand. But I am pretty use to now knowing what that glow should look like. It is quite dazzling bright - not just sort of bright. This click you hear? Make sure it is coming from the gas valve. Put your finger tips on it and feel, while you hear the click. If you hear a nice click, I have a feeling it is NOT the gas valve. That's MY opinion anyway. You can find out though. Here is how: Start the furnace sequencing. Then quickly run out to your gas meter and watch the fractional dial to see if it makes any sort of a jump. Do this several times to rule out something else in the house, causing this. If it jumps, you can almost be assured you need a new ignitor, as the likely cause. Some other problem could be from gas slots or ports in the vicinity of the ignitor are plugged up. The click sound is the valve trying to open. Just cause you don't smell gas doesn't mean anything. A furnace is drafting that gas odor away from you.
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