Have you look at the furnace controller "CPU" ? Some people call it computer. for me it is just a timing device monitors all safety switch and controls the gas valve to fire at the correct timing to heat up the house
There is a Self Diagnost LED indicator on the CPU. If fan running ok, Locate the "Red LED" on the CPU PCB, if it steady "ON" mean control circuit is ok,
if the LED is Flashs, count how many time,3 flashed=pressure switch not confirmed. 4 flashed =over heat, 5 flashe = some other switch is open,,,,,,,,,,if not Flashing LED it may be the inigtor not working,,,,,,
There is a Self Diagnost LED indicator on the CPU. If fan running ok, Locate the "Red LED" on the CPU PCB, if it steady "ON" mean control circuit is ok,
if the LED is Flashs, count how many time,3 flashed=pressure switch not confirmed. 4 flashed =over heat, 5 flashe = some other switch is open,,,,,,,,,,if not Flashing LED it may be the inigtor not working,,,,,,