I have a Lennox G40XH(X) series furnace and my ignitor never turns on (never burns). The fan comes on momentarily and then shuts itself off. The LED lights are flashing in fast mode which makes me think it's the ignitor... but because the fan shuts off so quickly, I think it may have something to do with that. I tried resetting/tapping any switches, re-engaging all the leads going to the fan and the ignitor, but no change. I changed my filter under 3 months ago...