P0A9C – Thermistor Fault

A thermistor fault is triggered detected if the analog voltage measured from the thermistor is outside of the normal thermal operating range. This error can be triggered if the temperature of the thermistor rises above 81C or drops lower than -41C. A shorted or open wire can result in artificially high or low measurements that would result in this error code. The use of an incompatible thermistor can cause inaccurate readings and trigger this error code.

When this error code is set, the Orion BMS will disregard the value of the affected thermistor, using the values of the other thermistors and continue to operate normally.


Resolving the issue:

Step 1. Check to ensure the thermistor / current sensor connector is plugged into the Orion BMS.

If the thermistor connector was not installed when the BMS was powered up, this error will result. Clear the error codes or restart the BMS if the connector was connected after the BMS was powered up.

Step 2. Download the freeze frame data using the Orion BMS utility.

The freeze frame data will indicate the temperatures measured by the BMS when the error was set. A thermistor reading -41 or +81 will indicate which thermistor set the fault. Ensure that the thermistor in question is actually connected to the BMS. If it was intentionally not connected, adjust the Orion BMS profile to indicate it is not populated.

Step 3. Check for shorts or open wires on the thermistors.

Using a multimeter with the thermistors disconnected from the Orion BMS, measure the resistance of the thermistor to ensure it is not fully shorted or open. If a thermistor is found to be shorted or open, correct the wiring error or replace the thermistor if faulty.

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Ewert Energy Systems, Inc
161 East St. Charles Rd
Carol Stream, IL 60188

Phone: (630) 868-3173
Fax: (866) 657-5667

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