I have a York Stellar furnace, age unknown, maybe 10-15 years. Once lit the furnace stays on until the cycle is complete, but won't re-light when the temp drops again. Flipping the switch off and then on makes it try to light again and sometimes it will, sometimes not. Seems like its only seconds away from lighting and then I hear it click and the ignitor shuts off and it won't try to light again until the switch or breaker is flipped off and on. I replaced the ignitor and tested the resistance, the new one had 48 ohms compared to the 103 ohms in the old one, after installed it worked for about a week with no problems, now its doing the same thing again.