Is your furnace turning on but shutting off unexpectedly? A dirty furnace flame sensor could be the culprit. This small but crucial component detects whether the burner is lit—if it’s covered in grime, your furnace may short-cycle or fail to stay on. The good news? Cleaning it is a quick and easy DIY fix that can save you from costly HVAC repairs. In this guide, we’ll walk you through how to clean a furnace flame sensor safely and effectively, with step-by-step instructions, essential tools, and maintenance tips to keep your heating system running smoothly. Quick Guide: How to Clean a Furnace Flame Sensor Turn Off Power & Gas – Shut off the furnace at the thermostat, power switch, and gas valve. Locate the Sensor – Find the thin metal rod near the burner assembly (usually held by one screw). Remove the Sensor – Unscrew it and gently disconnect the wire. Clean the Rod – Use fine-grit sandpaper (220+), a soft cloth, or rubbing alcohol to remove carbon buildup. Reinstall...