Potterton Generic Lockout (Legacy Boiler)

Boiler locked out with red light but no code on older Potterton models

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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

Flame failure, Overheat thermostat trip, Fan or air pressure switch fault, PCB fault

How to Fix / Troubleshooting

Safety first: Turn the boiler off and allow it to cool before attempting a reset.

User checks:

  • Press the reset button once (often a red or black button on the front panel) and observe whether the boiler restarts.
  • Check system pressure and gas supply as basic checks.

Engineer checks:

  • Follow the legacy Potterton fault-finding flowchart for lockout conditions.
  • Test ignition, flame sensing, overheat thermostat, fan, and air pressure switch sequentially.
  • Replace the faulty component (e.g., thermistor, APS, PCB) as identified.

Older non-digital Potterton boilers require systematic testing to identify lockout causes.

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Repair Difficulty

Hard 4/5

Required Part

Overheat Thermostat
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