E17
Ruud
Flow Sensor / Flow Switch Fault (Combi or Modulating Models)
Boiler shows E17 and may short‑cycle or fail to modulate correctly
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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
Stuck or scaled flow sensor, blocked strainers, incorrect sensor wiring, failed flow switch
How to Fix / Troubleshooting
Safety first: Turn off power and close isolation valves before removing any flow sensor or switch.
- Locate flow sensor/switch: On Ruud combi boilers, the DHW flow sensor is typically on the cold water inlet. System flow switches may be on the heating return.
- Clean strainers: Remove and clean any inlet strainers or filters to restore proper flow.
- Inspect sensor body: Remove the flow sensor and check for scale, debris, or damaged turbine/vanes. Clean gently and reinstall with new O‑rings if needed.
- Check wiring: Ensure the sensor connector is fully seated and wires are intact.
- Replace if faulty: If the sensor does not register flow correctly after cleaning, replace it with a Ruud‑approved part.
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Repair Difficulty
Medium
3/5
Required Part
DHW Flow Sensor / System Flow Switch
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