E1 n 21 (FJM Indoor) — Room temperature sensor error

What does E1 n 21 mean?

The FJM indoor unit displays E1 n 21, indicating an open or short circuit in the indoor unit's room temperature sensor. This prevents the unit from accurately detecting the room temperature.

• Faulty room temperature sensor
• Loose or damaged sensor wiring
• Issue with the indoor unit's PCB

Click steps to track your progress.

1. 1

   Turn off the power to the FJM indoor unit at the circuit breaker.

2. 2

   Visually inspect the room temperature sensor (often a small probe or part of the front panel) for damage.

3. 3

   Check the sensor's wiring connection to the indoor unit's PCB to ensure it is secure.

4. 4

   Restore power. If the error persists, contact a qualified technician to test or replace the sensor or PCB.