331
Takagi
Heat Exchanger Thermistor Failure
Takagi controller shows error 331; heater will not run.
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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
Defective heat exchanger thermistor, Broken thermistor lead, Poor connection at control board, Overheating damage to sensor
How to Fix / Troubleshooting
Safety first: Turn OFF power and gas. Allow the unit to cool completely.
Steps:
- 1. Locate heat exchanger thermistor: This sensor is attached directly to the primary heat exchanger body.
- 2. Visual inspection: Look for discoloration, melted insulation, or broken wires around the sensor. Check the connector at the PCB.
- 3. Reseat connector: Disconnect and reconnect the thermistor plug to ensure a solid connection.
- 4. Replace sensor: If the error remains, replace the heat exchanger thermistor with a genuine Takagi part. Mount it in the same position and ensure firm contact with the exchanger surface.
- 5. Test: Restore power and gas, clear the error, and run hot water to verify normal operation.
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Repair Difficulty
Medium
3/5
Required Part
Heat Exchanger Thermistor
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