How to tell if pilot light is out on gas furnace?

To determine whether the pilot light on a traditional gas furnace has extinguished, you can rely on both operational symptoms and a direct visual inspection. Operationally, the most prominent sign is that your heating system stops producing warm air entirely, leaving your living space cold despite the thermostat being adjusted to a higher temperature setting. To visually confirm, locate and remove the lower service access panel on the front of your furnace unit to gain access to the burner compartment. Look inside with a flashlight for the pilot assembly, which consists of a small metal tube where a tiny flame should be continuously burning. If no flame is visible, the pilot is out. Furthermore, you can verify this by checking whether the thermocouple is completely cool and whether the main burners fail to ignite when the thermostat calls for heat, confirming a lack of active pilot combustion.