Status LED shows code 12 (one short flash, two long flashes) after a call for heat; furnace may or may not complete a cycle.

Safety first: Turn off power before removing panels. Blower and inducer can start automatically.

On many Payne furnaces, code 12 indicates the blower ran after power-up or that the control is reporting a previous low-heat demand condition.

• Allow furnace to complete a full cycle: Set thermostat to HEAT and raise setpoint. Let the furnace run until it satisfies the thermostat and shuts off. Observe if the code clears to steady LED (normal operation).
• Check blower off-delay: The blower may continue to run after burners shut off. This is normal. Wait 60–120 seconds to see if the blower stops and the code clears.
• Inspect thermostat operation: If the thermostat is rapidly cycling the furnace (on/off every few minutes), adjust the cycle rate or replace the thermostat.
• Power reset: Turn off power for 1 minute, then restore. If the furnace operates normally and no other codes appear, no repair is needed.
• If code persists with erratic behavior: Inspect the control board for burn marks or swollen components. If present, the integrated furnace control (IFC) may need replacement.