BoilerFaultCodes Air Flow Device
The domestic water demand indicator will flash (approximately five times per second).
Worcester Bosch 25Si LPG Fault codes & diagnostics
7 fault codes with plain-English explanations, severity ratings, DIY guidance, and repair cost estimates.
Combi Gas 1999 onwards Discontinued
GC Number 47-311-50
Download the Worcester Bosch 25Si LPG manual
PDF
Versions & GC numbers
The fault code is already on your display
Note it down before pressing reset — resetting clears the code immediately. How to read fault codes →
Severity at a glance
Each cell = one fault code. Hover to identify. 7 Unrated
Which version do you have?
The GC number on your boiler's data badge identifies the exact appliance and production years, as recorded in the UK Product Characteristics Database.
| GC number | Appliance (register name) | Produced |
|---|---|---|
| 47-311-50 | 25Si - LL RSF | 1999–2002 |
Appliance names and production years are taken from the UK Product Characteristics Database (the SAP/SEDBUK register). Where a GC number is also printed in this model's own manufacturer manual, both sources were checked to agree.
Just want the most common Worcester Bosch 25Si LPG faults?
The top 6 problems in plain English — with causes, DIY checks and repair costs.
Fault codes
All 7 documented codes
Tap any card for details
Air Pressure Fault
Fan or flue related issue; check pressure switch operation, silicon tubes, flue restrictions, and wiring.
Burner Lockout
Boiler fails to ignite; check gas supply, spark electrode/HT leads, flame sensor, gas valve, and wiring.
Ignition Lockout
The central heating demand indicator will flash slowly (approximately once per second).
Overheat Cut-off
Both the central heating and the hot water demand indicators will flash together.
Primary Overheat
Boiler has overheated; check water pressure, venting of air, pump operation, primary sensor, and overheat thermostat.
Sensor Fault
Fault detected in DHW or CH sensor/wiring; check sensor continuity, resistance (1 kohm - 30 kohm), and fitting.