Suction Pipe Thermistor (Tho-S) Disconnected

What does E53 mean?

The suction pipe thermistor (Tho-S) on the outdoor unit is disconnected. This prevents the system from accurately monitoring suction line superheat, impacting operational safety, efficiency, and liquid floodback protection for the compressor.

• Suction pipe thermistor (Tho-S) is disconnected or has a broken wire.
• Faulty Tho-S sensor is providing an out-of-range reading.
• Incorrect installation or loose connection of the Tho-S sensor.

Click steps to track your progress.

1. 1

   Inspect the connector for the Tho-S thermistor on the outdoor unit PCB — verify it is securely seated.

2. 2

   Check the wiring connecting the Tho-S thermistor to the PCB for continuity and damage using a multimeter.

3. 3

   Verify the thermistor is correctly attached to the suction pipe for proper thermal contact.