Normal Furnace Startup

Sample of the typical Furnace start-up cycle. Most furnaces provide some LED codes to describe err conditions. One of the most common problems is a faulty ignitor. The pressure switch is less likely, but a possibility. If the pressure switch is working, most furnaces will continue to the burn cycle. If the ignitor is bad, you will hear the click of the gas valve and may briefly hear the gas start. It will quickly shut off because the furnace electronics know the gas didn't light. In this case, carefully remove the ignitor and inspect it without touching the element. If it's bad, you'll likely see a crack. *Disclaimer* I am not an expert. When in doubt, call a professional.