Error 121 — Indoor temperature sensor error (Short or Open)

What does 121 mean?

The indoor unit's temperature sensor is reporting an electrical fault, indicating either a short circuit or an open connection. This prevents accurate temperature readings.

• Faulty indoor temperature sensor
• Loose wiring to the sensor
• Damage to the sensor cable
• Corrosion on sensor terminals

Click steps to track your progress.

1. 1

   Turn off the power to the indoor unit at the main breaker.

2. 2

   Inspect the wiring and connection point of the indoor temperature sensor for looseness or damage.

3. 3

   If accessible, gently reseat the sensor's connector to ensure a firm connection.

4. 4

   Restore power to the unit and check if the error clears.

5. 5

   If the problem persists, the sensor may need replacement by a qualified technician.