Heater shows F7; may be associated with very low ambient temperatures.

Safety first: Turn off power before accessing sensors.

• Check actual temperature: Compare outdoor temperature to the heater’s displayed ambient reading. If they differ greatly, suspect the sensor.
• Inspect ambient sensor: On models with external ambient sensors, ensure the sensor is mounted in free air, away from direct sunlight or heater exhaust, and that its cable is intact.
• Protect from freezing: If the heater is in a freeze-prone area, ensure the circulation pump is running or the system is winterized.

If F7 appears in non-freezing conditions, the ambient sensor may need replacement.