What is a common symptom of a stuck gas valve in a furnace?

A common symptom of a stuck gas valve in a furnace is that the unit does not ignite or maintain a steady flame. When a gas valve is stuck in the closed position, gas cannot flow to the burners, causing the furnace to fail to ignite. If the valve is stuck open, it could lead to an unstable flame, which can also be dangerous. In either case, the furnace is unable to operate normally, resulting in a lack of proper heat production and inconsistencies in flame behavior.

This issue is critical because a functioning gas valve is essential for the safe operation of the furnace, ensuring that gas is delivered appropriately for combustion. If the gas valve fails, either by not opening or being unable to maintain a steady flow, it directly affects the furnace's performance and can lead to further safety concerns if not addressed.