TEMP SENSOR FAULT
OpenEVSE
Temperature Sensor Open/Short
Display shows 'TEMP SENSOR FAULT' or similar, unit may derate current or refuse to charge.
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Safety Warning
This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.
If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.
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Possible Causes
Broken thermistor lead on main board, Shorted temperature sensor, Damaged connector between CT board and main board, Firmware misconfiguration for sensor type
How to Fix / Troubleshooting
Safety first: Turn off power before touching internal boards. Do not bypass temperature protection permanently.
- Step 1 – Visual inspection: Open the enclosure and locate the temperature sensor (thermistor) on the main or CT board. Look for broken leads, cracked epoxy, or burnt areas.
- Step 2 – Connector check: If the sensor is on a separate CT board or daughterboard, reseat the connector between boards and ensure no pins are bent.
- Step 3 – Resistance measurement: With power OFF and sensor disconnected, measure the thermistor resistance at room temperature. Compare to OpenEVSE documentation (commonly 10k or 100k at 25°C). Infinite or near-zero resistance indicates a failed sensor.
- Step 4 – Replace sensor/board: If the sensor is discrete and replaceable, install a matching thermistor. If it is integrated, replace the entire main or CT board.
- Step 5 – Firmware verification: Using the LCD or Wi-Fi interface, confirm that the firmware is configured for the correct sensor type and that temperature readings look reasonable.
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Repair Difficulty
Medium
3/5
Required Part
Current Transformer (CT) Board
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