5101 (U3) — Air inlet thermistor or Compressor temperature thermistor open/short

What does 5101 (U3) mean?

This code indicates an issue with the air inlet thermistor (TH21) or the compressor temperature thermistor (TH4) in the outdoor unit. It suggests that the thermistor circuit is either disconnected or shorted, impacting temperature readings.

• Disconnection or contact failure of thermistor connectors.
• Characteristic defect of the thermistor itself.
• Defective outdoor multi controller circuit board.

Click steps to track your progress.

1. 1

   Inspect the connectors for the air inlet thermistor (TH21) and compressor temperature thermistor (TH4). Ensure they are securely connected and free from damage.

2. 2

   If possible, check the resistance of the thermistor using a multimeter. Compare it to expected values to determine if the thermistor is faulty.

3. 3

   If connections and thermistors appear correct, turn off the unit's power at the breaker, wait 30 seconds, and then restore power to reset.

4. 4

   If the error persists after these checks, professional inspection of the outdoor multi controller circuit board is recommended.