Indoor unit shows F1 and may run erratically or shut down.

Safety first: Turn off power to the indoor unit before removing covers.

Steps:

• Locate T1 sensor: The indoor ambient temperature sensor is usually clipped near the air intake or on the evaporator coil frame, with two small wires leading to the PCB.
• Check connection: Ensure the sensor plug is firmly seated on the indoor PCB and that wires are not cut or pinched.
• Inspect sensor: Look for physical damage to the sensor bulb or probe.

Repair: If wiring and connection look good but F1 persists, replace the T1 indoor temperature sensor. This is typically a plug-in part and can be replaced by a careful DIYer following the service manual.