5101 (1202) Temperature sensor fault - Return air temperature (TH21)

What does 5101 (1202) mean?

This error indicates a problem with the return air temperature sensor (TH21) in the indoor unit. It could be due to a faulty thermistor or a bad connection, leading to incorrect temperature readings for the return air.

• Defective thermistor (TH21).
• Loose or poor contact of the thermistor connector.
• Faulty indoor board if no other issues are found.

Click steps to track your progress.

1. 1

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

2. 2

   Check the connector for the TH21 thermistor on the indoor unit to ensure it is securely connected.

3. 3

   Visually inspect the thermistor's lead wire for any visible damage.

4. 4

   Restore power to the unit. If the error persists, note the ambient temperature.

5. 5

   A technician would typically check the thermistor resistance at different temperatures (e.g., 0°C, 10°C, 20°C, 30°C, 40°C) against specified values (15kΩ, 9.7kΩ, 6.4kΩ, 4.3kΩ, 3.1kΩ respectively).