Defro No Power / Electrical Supply Fault

Boiler does not start at all, display is blank, no lights or response.

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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

Blown internal fuse on Defro PCB, Tripped circuit breaker or fused spur, Faulty main power switch on Defro boiler, Loose mains connection block inside boiler

How to Fix / Troubleshooting

Safety: Electrical work should be done with the power isolated at the main breaker.

  • Check external supply: Verify that the circuit breaker or fused spur supplying the Defro boiler is on and that any fuse has not blown.
  • Test outlet: If the boiler is plugged in, test the socket with another appliance to confirm power is present.
  • Inspect mains terminal: With power off, remove the boiler's electrical cover and check that the live, neutral, and earth wires are securely clamped in the Defro mains terminal block.
  • Internal fuse: Many Defro PCBs have a replaceable fuse. If blown, replace only with the same rating. If it blows again immediately, a professional must locate the short circuit.
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Repair Difficulty

Medium 3/5

Required Part

Defro PCB fuse
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