E17
Termet
Three-Way Valve Positioning Fault
Boiler intermittently shows E17, especially when switching between CH and DHW, with unstable temperatures.
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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
Sticking three-way diverter valve in Termet hydraulic group, Faulty valve motor or microswitch, Limescale or debris in valve body, Wiring fault between valve motor and PCB
How to Fix / Troubleshooting
Safety first: Isolate power and close isolation valves before working on the hydraulic block.
User checks:
- Observe whether heating or hot water is available individually; if one mode works and the other does not, the diverter valve may be stuck.
- Reset the boiler once. If E17 persists, professional service is needed.
Technician checks:
- Inspect the three-way diverter valve for free movement; manually exercise if possible.
- Check the valve motor operation and end switches with a multimeter.
- Remove and descale or replace the diverter valve cartridge if obstructed.
- Verify correct wiring and control signals from the PCB.
After repair, test both CH and DHW modes to ensure correct valve operation.
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Repair Difficulty
Hard
4/5
Required Part
Three-Way Diverter Valve
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