Originally Posted by Houston204
Clean the flame sensor.
It will have a single wire connected to it.
Avoid the ignitor, it is easy to break and will also be located in front of the burners.
this. happens on all (older) gas furnaces from time to time. that little rod is inolved with flame rectification, dc voltage to ground through the flame. let's the furnace know that there is a flame so the call for heat (gas valve) remains on. once sut and corrosion builds up on the flame sensor it interferes with the sensing of the electrical signal the board needs to keep the call for heat on. It's telling the control board there is no flame so to cut the gas off.
anyways, hvac flame senser 101 over and out. easy monkeys. clean it and you will have heat. GoOd lUck.