E03
Attack Flue Gas / Air Pressure Switch Fault

Boiler shows E03 and does not start the burner; fan may run briefly then stop.

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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

Blocked flue or air intake on Attack balanced flue system, Faulty air pressure switch, Blocked or kinked silicone tubes to pressure switch, Faulty fan on Attack boiler

How to Fix / Troubleshooting

Safety: Turn off power. Do not operate the boiler with a suspected flue blockage—risk of carbon monoxide.

Steps:

  • Inspect flue terminal: Go outside and check the Attack boiler flue terminal. Remove any visible obstructions (leaves, nests, snow, ice). Ensure the air intake and exhaust are clear.
  • Check flue and air pipes: Visually inspect accessible sections of the concentric flue for damage, disconnection, or severe corrosion. Do not dismantle sealed flue sections unless qualified.
  • Inspect pressure switch tubing: Open the boiler casing and locate the air pressure switch and its silicone tubes. Ensure tubes are not split, kinked, or blocked with condensate. Blow gently through the tubes (with boiler off) to clear moisture.
  • Check fan operation: With the casing back on, power the boiler and listen for the fan. If the fan does not start or is very noisy, it may be failing.

Professional help: If E03 persists, an authorized Attack technician should test the pressure switch, fan speed, and verify flue integrity.

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Repair Difficulty

Hard 4/5

Required Part

Air Pressure Switch
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