Gas Furnace Help? Anybody a tech?

[losiXXXman]

My gas furnace is only igniting intermittently. The Integrated fan control is functioning normally, there is no issue with the blower(vent) motor. Resetting the gas control valve has helped sometimes, but not every time. Does this sound like an ignitor issue alone?

Really don't want to pay a service call fee, when I could order and replace the part myself....

[Coelacanth]

I had a similar issue with my furnace. I would hear it click a few times when it was expected to fire up, but after a few attempts over a period of several minutes, it would just stay off until the next cycle. In my case, it was indeed the ignitor. The technician came over, replaced the ignitor, and showed me something I could do to maintain it myself. After it's removed, it has a long, thin rod that's supposed to spark up or something when activated, but this rod gets carboned up. Last time my furnace did the clicky-clicky-no-fire, I removed the ignitor and gave the rod a good scuff with 400-grit sandpaper to remove any buildup and it has worked fine now for 2 more winters.

[TRX-1-3]

I had a "cycles no start" condition a time back and it was a dirty pilot light orifice (the tank had run empty and this was occuring after refill/purge), the gas stream was irregular and could not be ignited. But since yours is an intermittent scenario, I am not sure. Not sure what your setup is exactly and I am no furnace tech by any means, but my guess is some sort of dirty orifice..........er.......ignitor?

Mark

[Phin]

Your furnace use an electric hot surface igniter or a pilot light?

Sounds like the same problem I had twice with one of my furnaces. The electric igniter had a crack both times. (though I replaced the control panel the first time before I realized it was the igniter. ) They're easy to replace yourself but delicate. I'm not a tech but replaced mine myself the last time. Just make sure you don't touch the heating surface with your fingers...the oil can cause them to fail.

[Halgar]

You probably have a bad thermocoupler. Sometimes cleaning the carbon build up off of it will do the trick, most of the time not, but it's a place to start. The thermocoupler senses when there is flame, either by pilot light or burner light-up, which sends a signal to the gas valve to open or close, if there is no flame, the gas gets turned off so that there is no safety issues with asphyxiation or relocating your home down the street in a big fiery ball of flame.

The other thing I'd check is the quality of the connections of the thermostat, both at the thermostat and the furnace. Thermostats also go bad and start sending faulty signals, though, short of replacement, I don't know if there is a way to test them.

If you do end up hiring someone, call at least three different companies, explain the problem, and get their opinion and projected fees over the phone. Also ask them if they give cash discounts, discounts for Yelp users, etc. I had some work done in November and the bill dropped 10% because I asked.

[jwscab]

Definitely follow phins and Halgars advice. If its a hot surface igniter, check to see if there is a white/ yellow residue in one small area of the element that is a dead giveaway it is cracked. I had to replace mine twice. Easy enough but do not touch the element, like a halogen work lamp.

[DMAT]

guess im not the only one hit with this bug.

got a call at work that the heater isnt turning on. just getting a single click when using the thermostat to tell it to turn on. it was running a few weeks ago without issue. I'm guessing its the pilot light at moment but wont know at all until I get home.

we just had about 10-11 days straight of on and off rain with 90%+ humidity too.

[SFC K]

You probably have a bad thermocoupler. Sometimes cleaning the carbon build up off of it will do the trick, most of the time not, but it's a place to start. The thermocoupler senses when there is flame, either by pilot light or burner light-up, which sends a signal to the gas valve to open or close, if there is no flame, the gas gets turned off so that there is no safety issues with asphyxiation or relocating your home down the street in a big fiery ball of flame.

The other thing I'd check is the quality of the connections of the thermostat, both at the thermostat and the furnace. Thermostats also go bad and start sending faulty signals, though, short of replacement, I don't know if there is a way to test them.

If you do end up hiring someone, call at least three different companies, explain the problem, and get their opinion and projected fees over the phone. Also ask them if they give cash discounts, discounts for Yelp users, etc. I had some work done in November and the bill dropped 10% because I asked.

I agree, this is probably your culprit. We have dirty gas in our area, so every year I have to pull out the Flame sensor probe and lightly clean it with 2000 grit finishing paper and install it back into the furnace. Works every time. I always know instantly when it gets dirty, because the furnace blower motor will start for a few seconds, igniter will light up, then the flame kicks on for a few seconds and goes out shortly thereafter. It will try the same sequence over and over until it stays lit or clean it.

When you look into your furnace where the burner plate is, you will see a flame sensor probe (Thin metal shaft about 2-3" long with a slight bend in it)where the flame kicks on. They usually are held in place with one screw.

Good luck!

[Coelacanth]

Troubleshooting a faulty flame sensor probe and ignitor is easy enough; if the furnace fires up briefly, then shuts off, it's the flame sensor that's the culprit--because it doesn't detect that it's turned on already. It's intended to keep from re-igniting when the furnace is already fired up.

If the furnace repeatedly tries to start but doesn't fire up, however, it's more likely to be the ignitor...at least, that's the easiest thing to check. As the ignitor wears and gets more fouled by carbon, the performance degrades. Mine would click, sometimes it would fire up, sometimes it wouldn't...and then it would get fire up more and more infrequently, until one evening, it didn't fire up at all. I don't believe it's a part that just suddenly fails, it tends to get more and more problematic over time.

Does your furnace model have LED lights that flash error codes? Mine is a Lennox and the green LED lights flash in different patterns to indicate normal and error conditions. Check that out in your user manual (or Google your model's owner's manual) and see what the troubleshooting diagnostic tree tells you. That gave me pretty clear clues that my culprit was the ignitor, not the flame sensor.

http://www.webhvac.com/2011/01/lennox-gas-furnace-troubleshooting/

Won't fire > Ignitor
Won't stay on > Flame sensor