Vaillant No Power / Dead Boiler

Boiler will not start at all, no display or lights

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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 fuse at fused spur, Tripped circuit breaker, Faulty power supply cable, Failed main PCB

How to Fix / Troubleshooting

Safety: Do not open the boiler casing unless you are competent. Electrical work should comply with local regulations.

  • Check fused spur: Ensure the boiler’s switch is on and the fuse (typically 3A) is intact. Replace only with the correct rating.
  • Check consumer unit: Confirm the circuit breaker for the boiler circuit has not tripped.
  • Verify power at spur: Plug in a lamp or tester at the spur (if socket type) to confirm power is present.
  • Engineer diagnosis: If power is present but the boiler is dead, the internal fuse or PCB may have failed and needs professional attention.
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Repair Difficulty

Medium 3/5

Required Part

Main Control PCB
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