Thermostat shows F02 and the indoor temperature reading is obviously incorrect

Safety first: Turn off power to the HVAC system before removing the thermostat from the wall.

• Check thermostat location: Ensure the thermostat is not in direct sunlight, above electronics, or directly in the path of a supply vent. Relocate if necessary to an interior wall away from drafts.
• Inspect wiring: Remove the thermostat and check that all low-voltage wires are firmly attached and not shorting together. Tighten any loose terminals.
• Compare temperature readings: Use a separate room thermometer to compare the thermostat reading. If the thermostat is off by a large margin and F02 is displayed, the internal sensor is likely bad.
• Replace thermostat: Install a new compatible thermostat if the sensor is defective. Follow American Standard wiring diagrams to ensure correct connections.