Unit stops cooling and displays E04; may occur after long operation.

Safety first: Isolate power at the breaker before accessing internal components.

• Step 1 – Access thermistor: Remove the front panel and filter. Carefully remove the plastic covers to expose the evaporator coil. Locate the small sensor clipped to the coil (usually in the middle).
• Step 2 – Inspect sensor and wiring: Ensure the thermistor is firmly clipped to the coil and the wires are not cut or pinched. Follow the harness back to the indoor PCB and check the connector is fully inserted.
• Step 3 – Resistance check: Disconnect the thermistor and measure its resistance with a multimeter. Compare to Toshiba service data (typically 5–20 kΩ depending on temperature). Infinite or near-zero resistance indicates a bad sensor.
• Step 4 – Replace thermistor: If readings are out of range, replace the indoor coil temperature sensor with a Toshiba-compatible part. Route the new harness away from sharp metal edges.
• Step 5 – Reset and test: Reassemble, restore power, clear the error by power-cycling, and run in cooling mode to confirm normal operation.