5101, 5102, 5103 — Indoor thermistor trouble (Air inlet, Liquid pipe, or Gas pipe)

What does 5101 mean?

These codes indicate a problem with one of the indoor unit's thermistors (temperature sensors) — specifically, TH21 for air inlet (5101), TH22 for liquid pipe (5102), or TH23 for gas pipe (5103). The sensor is detected as either open-circuited or short-circuited, meaning it cannot properly detect and report temperature.

• Loose or disconnected wiring to the specific thermistor.
• A faulty thermistor itself (characteristic defect).
• Contact failure of the thermistor connectors.
• A problem with the indoor controller board.

Click steps to track your progress.

1. 1

   Turn off the main power to the indoor unit at your electrical breaker for safety.

2. 2

   Carefully inspect the wiring connections to the specific thermistor indicated by the code (TH21 for 5101, TH22 for 5102, TH23 for 5103) to ensure they are securely connected and not loose.

3. 3

   Gently push in on any connectors to ensure a firm contact.

4. 4

   Restore power to the unit and observe if the error clears. If not, a qualified technician will be needed to test the thermistor's resistance or replace it.