Sime Temperature Fluctuation / Poor Modulation

Water heater output temperature fluctuates between very hot and cold during a single shower.

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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

Faulty DHW NTC sensor, Unstable gas supply, Flow sensor reading incorrectly, Oversized or undersized water flow through heater

How to Fix / Troubleshooting

Safety: Risk of scalding. Be cautious when testing hot water.

Steps:

  • Stabilize flow: Open only one hot tap and keep it at a constant position. Avoid mixing large amounts of cold water at the tap; instead, set the desired temperature on the heater.
  • Clean flow sensor: Remove and clean the flow sensor/turbine to ensure accurate flow measurement.
  • Inspect DHW NTC: Check that the outlet sensor is firmly attached and not loose or corroded.

Professional help: Persistent fluctuations may require sensor replacement or gas valve/control board diagnostics by a technician.

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Repair Difficulty

Medium 3/5

Required Part

DHW NTC Sensor and Flow Sensor
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