Biasi Garda M90f Fault codes & diagnostics

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

Combi Natural Gas 24 kW 2002-2007 Discontinued
GC Numbers 41-970-1147-970-2041-970-1047-970-19

Replaced by: Garda HE

Download the Biasi Garda M90f manual The official installation & service manual (PDF) — the exact document these fault codes were verified against. PDF

The fault code is already on your display

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

Versions & GC numbers

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
41-970-11 Garda M90F. 28SR 2002–2007
47-970-20 Garda M90F. 28S 2002–2007
41-970-10 Garda M90F. 24SR 2002–2007
47-970-19 Garda M90F. 24S 2002–2007
Just want the most common Biasi Garda M90f faults?
The top 6 problems in plain English — with causes, DIY checks and repair costs.
Fault codes

All 4 documented codes

Tap any card for details

All Lamps OFF

Your boiler appears to have no electrical power at all, meaning the screen and lights are completely blank.

High DIY-safe £120-350

What to check first

  1. Check if the boiler's power switch is turned on
  2. Check your home's main fuse box (consumer unit) for a tripped circuit breaker
  3. Check the fuse in the spurred power socket next to the boiler

Parts commonly replaced

  • Electronic Control PCB
  • Internal Fuse
  • Mains Cable
Full explanation for All Lamps OFF
All Lamps ON

Your boiler's internal computer has suffered a critical failure and can no longer control the heating or hot water functions.

High Engineer only £250-£400

Parts commonly replaced

  • Main Printed Circuit Board (PCB)
Full explanation for All Lamps ON
Lock---out signal lamp red

Your boiler is failing to recognise that the flame has lit, causing it to repeatedly try to spark before shutting down for safety.

High Engineer only £100-240

Parts commonly replaced

  • Flame sensing electrode
  • Ignition lead
  • Printed Circuit Board (PCB)
Full explanation for Lock---out signal lamp red
lock-out light

Your boiler has shut down for safety because it either failed to light, sensed it was getting too hot, or detected an issue with how it clears waste gases.

High DIY-safe £100-350

What to check first

  1. Check that your gas pre-payment meter (if applicable) has credit.
  2. Ensure any external gas isolation valves are fully open.
  3. Press and release the reset button on the front control panel to see if the boiler restarts.

Parts commonly replaced

  • Ignition Electrode
  • Safety Thermostat
  • Air Pressure Switch
  • Gas Valve
Full explanation for lock-out light
Status & diagnostic codes

4 operating states & engineer diagnostics

Not faults — these are normal operating states. Tap to expand.

1 second ON 1 second OFF Status Your boiler has detected that the temperature is low and is running its internal protection mode to prevent the pipes from freezing. 10 Diagnostic Your boiler has detected an issue with the air intake or exhaust system, which prevents it from operating safely. 12 Diagnostic Your boiler has detected an issue with the electrical circuit board or its internal wiring, preventing it from operating correctly. A short pulse every 4 seconds Status Your boiler is currently switched off but is monitoring the temperature to prevent the internal pipes from freezing.