C16
Bosch EasyControl Boiler Lockout Reported to EasyControl

Bosch EasyControl shows error C16 and indicates that the boiler safety lockout has been triggered via the control interface.

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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

Boiler internal fault (flame failure, overheat, low pressure), EasyControl receiving lockout status over bus, Boiler reset not performed, Persistent boiler hardware issue

How to Fix / Troubleshooting

Safety first: Follow boiler safety instructions. Do not attempt to bypass safety devices.

  • 1. Check boiler display: Go to the boiler and read its own error code or status. The EasyControl is only reporting what the boiler sends.
  • 2. Reset boiler: If the boiler manual allows, press the reset button once and observe operation. Do not repeatedly reset a boiler that immediately locks out again.
  • 3. Check system pressure: Ensure the heating system pressure is within the recommended range (typically 1.0–1.5 bar when cold). Top up via the filling loop if permitted by the manual.
  • 4. Vent radiators: Bleed air from radiators if there are cold spots or gurgling noises, then re-check pressure.

Professional help: If the boiler continues to lock out or shows its own error code, a Gas Safe / qualified heating engineer must diagnose and repair the boiler fault.

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Repair Difficulty

Medium 3/5

Required Part

Boiler safety and control board
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