391
Takagi
Mixing Thermistor Failure (if equipped)
Takagi water heater shows error 391; unit will 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
Defective mixing thermistor, Loose or corroded connector, Damaged wiring harness, Water intrusion at mixing valve area
How to Fix / Troubleshooting
Safety first: Turn OFF power and gas. Allow the unit to cool.
Steps:
- 1. Identify mixing thermistor: On models with built-in mixing or recirculation, the mixing thermistor is mounted near the mixing valve assembly.
- 2. Inspect wiring and connector: Look for corrosion, moisture, or broken wires. Dry any moisture and reseat the connector.
- 3. Check for leaks: Inspect around the mixing valve and nearby piping for leaks that could affect the sensor. Repair leaks first.
- 4. Replace sensor: If the error persists, replace the mixing thermistor with a genuine Takagi part.
- 5. Test: Restore power and gas, clear the error, and run hot water to confirm proper operation.
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Repair Difficulty
Medium
3/5
Required Part
Mixing Thermistor
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