A18
Fondital
Diverter Valve Position Fault
Error A18, unit may shut down when switching between DHW and heating.
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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 diverter valve, Faulty diverter motor/actuator, Scale or debris in hydraulic block, Position microswitch failure
How to Fix / Troubleshooting
Safety: Turn off power and isolate water before removing hydraulic components.
- Operate taps and heating: Observe whether the unit can switch correctly between hot water and heating. If one mode works and the other does not, suspect the diverter valve.
- Check actuator: Listen for the diverter motor when changing modes. No sound may indicate a failed motor or no power.
- Clean valve: A technician can remove the diverter valve cartridge from the hydraulic block and clean or replace it if scaled or jammed.
- Microswitches: Inspect any end‑position switches for proper operation and secure wiring.
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Repair Difficulty
Hard
4/5
Required Part
Diverter Valve Assembly
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