Most of today’s gas furnaces have electronic ignition systems rather than pilot lights on older furnaces. If you own a furnace that has an electronic igniter, you can’t manually light it.
The two types of electronic ignition switches are hot surface and intermittent pilot ignition. Hot surface switches use element and intermittent pilot switches to create an electric spark to light the pilot. So if you have a newer heating system that won’t start and the temperature drops in your home, chances are it’s due to the ignition system. But why is it out?