Discharge Thermistor Short/Open

What does U3 mean?

The compressor discharge thermistor, which monitors compressor discharge temperature, is detected as either short-circuited or open-circuited. This prevents accurate temperature measurement and compromises the system's ability to protect the compressor from overheating.

• Discharge thermistor (49C) is shorted or open.
• Faulty temperature sensor in the discharge line.
• Wiring fault to the discharge thermistor.

Click steps to track your progress.

1. 1

   Measure the resistance of the discharge thermistor at its leads — compare to a resistance-temperature chart if available.

2. 2

   Inspect the thermistor's wiring and connector on the outdoor unit PCB for damage, corrosion, or secure seating.

3. 3

   Verify the thermistor is correctly seated and making good thermal contact with the compressor discharge pipe.