Occasionally, my furnace ignites for a few seconds then goes out. A few seconds later it ignites again then goes out and doesn't try to ignite again. During this the little blower is going and the igniter is glowing until after the second attempt. All burners ignite each time. Sometimes the furnace stops after it's been lit and working fine. When this happens the large hvac blower continues to run for hours even though everythings cold. I have to turn everything off and wait about 30 seconds before turning it back on. I inspected what I think is the flame detector (long SS wire in the burner farthest from the igniter) and it looks fine. There is another item that looks like a resistor in a ceramic housing mounted back near the access panel. Not sure what this is, but it looks corroded. Any ideas? This has been going on for 7 years. I've had many technicians out and they all have different ideas, I pay them, but the problem returns.

Try cleaning your flame sensor with steel wool or sandpaper.