Abnormal High Discharging Temperature / Inner Thermostat (49C) Operation

What does U2 mean?

The compressor discharge temperature is excessively high OR the internal thermostat (49C) on the outdoor unit has activated due to an over-temperature condition. Both indicate an overheating issue within the outdoor unit or its components, risking compressor damage.

• High discharge temperature detected.
• Operation of the inner thermostat (49C).
• Overheating condition in the discharge line.

Click steps to track your progress.

1. 1

   Measure discharge pressure and temperature at the compressor outlet using appropriate gauges and probes.

2. 2

   Verify condenser coil cleanliness and ensure unrestricted airflow over the coil and around the compressor.

3. 3

   Check refrigerant charge using manifold gauges and subcooling/superheat calculations — ensure it's not overcharged.

4. 4

   Measure the temperature of the compressor casing using an infrared thermometer.

5. 5

   Verify the operation and rotation direction of the outdoor fan motor.