Thermostat shows H2 and indicates low indoor temperature beyond normal range; heating may run continuously or lock out.

Safety first: If the home is very cold, protect pipes from freezing and avoid using unsafe supplemental heaters.

• Verify room temperature: Compare thermostat reading with a separate thermometer. If the thermostat reads much lower, suspect drafts or sensor issues.
• Seal wall opening: Remove the thermostat and seal gaps in the wall box with non‑flammable insulation or foam to prevent cold air from the wall cavity affecting the sensor.
• Relocate thermostat if needed: If installed on an exterior wall or near an entry door, consider relocating to an interior wall.
• Check heating equipment: If the room truly is cold and the furnace/air handler is not running, there may be a separate equipment fault. Check for error codes on the Payne furnace and call a technician if needed.
• Replace thermostat: If H2 persists with normal room temperature and good location, replace the thermostat due to a faulty sensor.