Thermistor fault

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The thermistor input on an option board has detected an increase in motor temperature beyond safe limits, or the input itself is not properly terminated if unused. This indicates potential motor overload or inadequate motor cooling. Overheating can severely damage the motor windings, reduce motor lifespan, and lead to efficiency losses.

• Motor winding temperature exceeding the thermistor's trip threshold due to sustained overload or insufficient cooling (e.g., clogged motor fan).
• Broken thermistor wiring between the motor and the drive's option board, resulting in an open circuit detection (high resistance).
• Incorrect connection or termination of the thermistor input terminals (e.g., T1, T2) on the option board if the feature is unused.
• Shorted thermistor wiring or a faulty thermistor indicating an abnormally low resistance (overtemperature condition).

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1. 1

   Measure the resistance of the motor thermistor directly at the drive's option board terminals (e.g., T1, T2) using a multimeter. Compare to known thermistor curves (e.g., PTC type ~250Ω cold, ~4kΩ hot).

2. 2

   Inspect motor cooling fan operation and clear any debris from the motor's cooling fins.

3. 3

   Verify proper wiring and shielding of the thermistor cable from the motor to the drive's option board. Check for breaks or shorts.

4. 4

   If the thermistor input is unused, ensure it is properly terminated with a jumper wire or a fixed resistor (e.g., 2.2kΩ) as specified in the drive manual.

5. 5

   Monitor motor current (P0-01) and motor temperature (if available via P0-02 or separate sensor) to confirm actual thermal load.