501
Ariston Ignition Lockout (No Flame)

Boiler displays 501, ignition lockout, red LED on, no flame

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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

No gas supply, Blocked burner, Faulty ignition electrode or lead, Faulty gas valve or PCB

How to Fix / Troubleshooting

Safety: Turn off the boiler and gas supply if you smell gas. Ventilate the area and contact a Gas Safe engineer.

  • Check gas supply: Confirm other gas appliances work. If not, contact your gas provider.
  • Reset boiler: Follow the manual to reset. If 501 returns repeatedly, do not keep resetting.
  • Condensate pipe: In freezing weather, check the external condensate pipe for ice blockage. Thaw gently with warm (not boiling) water and lag the pipe.
  • Engineer tasks: An engineer will inspect and clean the burner, check the ignition electrode, test the gas valve, and verify combustion.
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Repair Difficulty

Professional Required 5/5

Required Part

Gas Valve
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