Error 399 — Heat sink temperature sensor error of Fan2

What does 399 mean?

A fault has been detected with the heat sink temperature sensor for Fan2 in the outdoor unit. This sensor is crucial for monitoring the temperature of the fan's power components, and an error can indicate overheating.

• Faulty heat sink temperature sensor for Fan2
• Loose sensor connection or damaged wiring
• Overheating of Fan2 components due to other factors
• Control board fault preventing accurate sensor reading

Click steps to track your progress.

1. 1

   Turn off power to the outdoor unit at the main electrical panel.

2. 2

   Locate Fan2 and its associated heat sink temperature sensor.

3. 3

   Inspect the sensor's wiring and connections for any signs of looseness or damage.

4. 4

   Ensure the sensor is properly installed and making good contact with the heat sink.

5. 5

   Restore power and check if the error is resolved. If not, the sensor or its wiring likely needs professional replacement.