An igniter is a small electrical component in a gas furnace that heats up to an extremely high temperature to light the burner. In modern Mobile Home Gas Furnaces, "Hot Surface Igniters" (HSI) have replaced the old-fashioned standing pilot light, which saves energy by only running when needed. These are usually made of silicon carbide or silicon nitride and are very fragile; they can crack if touched with bare hands. We stock a wide variety of replacement igniters for ACIq and other major brands in our Parts department. If your furnace won't start and you don't see a glowing light during the startup sequence, the igniter is likely the culprit. This is one of the most common repair parts for any Ducted heating system. Having a spare on hand is a smart move for homeowners to avoid a cold house during a winter holiday. It is the "spark plug" of your home's heating system.