Boiler Fault Codes Guide

Understand what your boiler error codes mean and what action to take. Our experts can fix any fault across all brands.

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About Boiler Fault Codes

When your boiler detects a problem, it displays an error code on the control panel. These codes help engineers quickly identify the issue. While many faults require professional repair, some simple steps can sometimes resolve the problem.

If you see a fault code, try resetting the boiler (consult your manual for instructions). If the fault persists, contact us immediately. Never ignore persistent fault codes, as they indicate a safety or performance issue requiring professional attention.

Common Boiler Fault Codes

E119

Worcester Bosch

Ignition failure

Ignition electrode may need replacement. Gas supply issue possible.

E120

Worcester Bosch

Boiler shutdown

Usually indicates a temporary fault. Try reset. If persists, call for service.

F22

Vaillant

Low water pressure

Top up system via filling loop. If pressure drops repeatedly, there may be a leak.

F28

Vaillant

Ignition fault

Try reset. If continues, thermostat or gas supply issue may exist. Contact engineer.

119

Ideal

Ignition failure

Check pilot light. If no ignition after reset, electrode cleaning or replacement needed.

118

Ideal

Low gas pressure

Check gas supply. May indicate regulator fault. Contact emergency services if smell gas.

Common Boiler Problems & Solutions

1

Boiler Won’t Ignite

If your boiler is failing to ignite, the ignition electrode may be dirty or faulty. The gas supply might also be interrupted.

  • Check if pilot light is lit (if visible)
  • Verify gas supply is turned on
  • Try resetting the boiler
  • If still not working, call our engineers
2

Low Water Pressure

Boiler pressure should typically read between 1–2 bar. If lower, your boiler may lose heat or shut down.

  • Locate the filling loop or valve
  • Open it slowly to add water
  • Stop when pressure reaches 1.5 bar
  • If pressure drops again, there’s a leak – call us
3

Pilot Light Keeps Going Out

If the pilot light repeatedly extinguishes, the thermocouple (a safety device) may be faulty or dirty.

  • Try relighting the pilot
  • If it goes out within minutes, it’s a thermocouple issue
  • This requires professional replacement
  • Do not attempt to repair yourself
4

Boiler Keeps Shutting Down

Multiple shutdowns suggest safety lockouts from overheating, low pressure, or fault detection.

  • Allow boiler to cool for 30 minutes
  • Check water pressure is adequate
  • Ensure flue is not blocked
  • If problem persists, professional help needed
5

No Hot Water (But Heating Works)

If heating works but there’s no hot water, the diverter valve or three-way valve may be stuck or faulty.

  • Try resetting the boiler
  • Check the thermostat isn’t set too low
  • Run all hot taps for 1–2 minutes
  • If no improvement, diverter valve needs service
6

Unusual Noises or Smells

Banging, whistling, or chemical smells indicate problems requiring immediate professional attention.

  • Turn off boiler immediately if smell gas
  • Call emergency services if strong gas smell
  • Banging often indicates air in system
  • Call our engineers to diagnose safely

Need a Heating Service?

Call us 24/7 for repairs, maintenance, or to discuss any heating needs. Our Gas Safe engineers are ready to help.

📞 Call 07865 741986