321
Takagi Inlet Thermistor Failure (Open or Short)

Error 321 appears on the Takagi remote; unit does not operate.

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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

Failed inlet thermistor sensor, Loose or corroded thermistor connector, Damaged sensor wiring, Water damage at inlet area

How to Fix / Troubleshooting

Safety first: Turn OFF power and gas. Let the heater cool.

Steps:

  • 1. Locate inlet thermistor: Usually mounted on or near the cold water inlet pipe inside the unit.
  • 2. Inspect harness and connector: Check for loose connections, corrosion, or broken wires. Reseat the connector at both the thermistor and PCB ends.
  • 3. Check for leaks: Inspect the cold inlet fittings and internal piping for leaks that could drip onto the sensor. Repair any leaks first.
  • 4. Replace inlet thermistor: If wiring is intact but error persists, replace the inlet thermistor with the correct Takagi part. Secure it firmly to ensure good thermal contact.
  • 5. Restore service: Turn power and gas back on, clear the error, and test operation.
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Repair Difficulty

Medium 3/5

Required Part

Inlet Thermistor
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