I just recently moved into an old row house (built in the late 1800's) and have an issue with the gas furnace. I was told that the furnace did not work so I had the local gas company come out to do a safety check and light. They don't troubleshoot or repair and they let me know that upfront. So the gas company guy climbs under the house where the furnace is. He immediately sees that the ignitor (spark type, not glow plug) isn't wired up. To my surprise he wires it up and tries to start the furnace. No spark. So he follows the power cord to an outlet and finds that it's barely plugged in. Still no spark. He then tells me that the ignitor control board (Fenwall) is probably bad, and said they are usually cheaply made. But he tries one more thing and unplugs a socket that goes from the ignitor control box to the ignitor, blows it out with some air, plugs it back in and voila! It immediately sparks and the furnace lights. I have heat! For a little while, because later in the day I noticed that the furnace is no longer kicking on. I climb under the house, unplug the furnace from the outlet and start jiggling wires to see if something is loose. Then plug the power cord back in a voila! Sparking and then gas flame. So it goes like this for a while, sometimes the furnace works for a few hours, sometimes for a few days. So I come to find out that it doesn't seem to matter if I unplug the power from the outlet or if I unplug the connector to the ignitor, that fixes the issue and it will immediately start to spark and light. I tried shutting off the circuit breaker to see if that would work, and make things easier than climbing under the house every time I want to relight the furnace, but that never works! This is a puzzling problem, why unplugging the power cord works but not tripping the breaker. I don't think the problem is the control board because unplugging and plugging the connector that goes to the ignitor fixes the issue too. I could be wrong and this why I'm asking for any help or ideas. Thx!