American Standard thermostat displays F01 and will not control the air conditioner

Safety first: Turn off power to the HVAC system at the breaker before removing the thermostat.

• Reboot thermostat: Remove the thermostat from its wall plate. If it has batteries, remove them for 30 seconds, then reinstall. If it is powered by the system, leave it off the wall for 1–2 minutes, then reconnect.
• Check power to thermostat: Ensure the R and C wires are properly connected and not loose or corroded. If the display is dim or flickering, there may be a low-voltage power issue.
• Verify compatibility: Confirm that the thermostat model is approved for use with American Standard air conditioners and heat pumps. Incompatible stats can show fault codes and misbehave.
• Replace thermostat if F01 persists: If rebooting and wiring checks do not clear F01, the thermostat is likely defective and should be replaced with a compatible American Standard or equivalent smart thermostat.