A failed furnace ignitor is one of the most common causes of a furnace lockout. Replacing it is a straightforward DIY task that can save you upwards of $300 in HVAC service fees. In this guide, I’ll walk you through how to identify a burnt-out ignitor, the essential safety steps to take before you begin, and a step-by-step replacement process to get your home warm again. Quick Guide: How to Replace Your Furnace Ignitor 1. Cut the Power and Gas: Flip the furnace service switch to OFF and turn the manual gas valve handle so it is perpendicular to the pipe. 2. Open the Cabinet: Remove the furnace access panels to locate the burner assembly and the ignitor (look for the wires leading to a small ceramic base). 3. Unplug the Harness: Gently squeeze and pull the plastic wire connector to disconnect the old ignitor from the furnace. 4. Remove the Mounting Screw: Using a nut driver or screwdriver, remove the single screw holding the ignitor bracket in place and carefully slide the o...