E18
Dimplex Over-Temperature Differential / Control Instability

E18 displayed; unit cycles on and off rapidly and cannot maintain set temperature

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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

Incorrect temperature setpoint, Restricted flow causing rapid temperature rise, Faulty mixing valve downstream, Control PCB algorithm fault

How to Fix / Troubleshooting

Safety: Beware of scalding water when testing.

  • Adjust setpoint: Reduce the temperature setpoint on the Dimplex control panel to a moderate level (e.g., 45–50°C) and retest.
  • Check flow rate: Ensure adequate flow through the heater by fully opening the hot tap and cleaning aerators and shower heads.
  • Inspect mixing valve: If a thermostatic mixing valve is installed, verify it is not stuck or restricting flow. Service or replace if necessary.

Note: If E18 persists with good flow and normal setpoint, the control PCB may be faulty and should be evaluated by a technician.

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Repair Difficulty

Medium 3/5

Required Part

Thermostatic Mixing Valve / Main Control PCB
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