Indoor unit displays F1, unit may run but with poor temperature control

Safety first: Turn off power to the indoor unit before accessing the control box.

• Locate the room sensor: The T2 sensor is usually near the air intake grille or behind the front panel. It is a small thermistor on a wire harness.
• Check connection: Follow the sensor wires to the PCB and ensure the connector is fully seated and not corroded.
• Inspect sensor: Look for physical damage, cuts, or crushed wires. If damaged, replace the sensor with the Tosot-specified part.
• Replace if error persists: If F1 remains after reseating, replace the room temperature sensor. Clear the error by power cycling.