Worcester Bosch Highflow CDi Fault codes & diagnostics

2 fault codes with plain-English explanations, severity ratings, DIY guidance, and repair cost estimates.

Combi Natural GasLPG 29-44 kW 2007-2019 Discontinued
GC Numbers 47-108-1147-108-12

Replaced by: Greenstar 8000 Lifestyle

The fault code is already on your display

Note it down before pressing reset — resetting clears the code immediately. How to read fault codes →

Fault codes

All 2 documented codes

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Light off

Your boiler is currently sitting in standby mode because it hasn't received a signal from your thermostat or timer to start heating.

Low DIY-safe £0-120

What to check first

  1. Check that your room thermostat is turned up higher than the current room temperature.
  2. Ensure your programmer or heating timer is set to 'ON' or 'Auto'.
  3. Replace the batteries in your wireless wall thermostat if the screen is blank.

Parts commonly replaced

  • Room thermostat
  • External programmer
  • Wireless receiver
Full explanation for Light off
Light on

Your boiler is working normally and is currently heating your home or water as requested.

Low DIY-safe

What to check first

  1. No action is required as this is a status indicator, not a fault.
  2. If the light is on but your radiators are cold, check that your room thermostat is turned up.
  3. Ensure your programmer or timer is set to an 'on' period.
Full explanation for Light on