Navien
Temperature Fluctuation / Short Cycling
Intermittent hot water: temperature fluctuates between hot and cold during a shower without any error code.
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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
Minimum flow not maintained by low-flow fixtures, Dirty flow sensor causing erratic readings, Scale buildup in heat exchanger, Faulty outlet temperature sensor or mixing valve
How to Fix / Troubleshooting
Safety: Use caution when water temperature is unstable to avoid scalding.
Steps:
- 1. Test at a high-flow faucet: Run hot water at a tub or laundry sink. If temperature is stable there, the issue may be with low-flow shower heads or mixing valves.
- 2. Clean inlet filter and flow sensor: Remove sediment from the inlet filter and clean the flow sensor turbine to improve flow measurement.
- 3. Descale heat exchanger: Perform a descaling flush if maintenance is overdue; scale can cause rapid overheating and burner cycling.
- 4. Check recirculation settings (if equipped): Incorrect recirculation mode or timer settings can cause temperature swings; review the Navien manual and adjust.
If fluctuations persist after cleaning and descaling, a technician should test the outlet thermistor and internal mixing valve.
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Repair Difficulty
Medium
3/5
Required Part
Primary Heat Exchanger
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