Biasi Garda M90f Fault codes & diagnostics

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

Combi Natural Gas 24 kW 2002-2007 Discontinued

Replaced by: Garda HE

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.
5 High 2 Low
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 7 documented codes

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1 second ON 1 second OFF

Your boiler is operating normally and is currently switched on to provide heating or hot water as requested.

Low DIY-safe £0

What to check first

  1. No action is required as this light sequence indicates the boiler is functioning correctly.
  2. If you have no heating or hot water despite this light, check that your room thermostat is turned up.
  3. Ensure your gas supply is active and the boiler pressure is between 1 and 1.5 bar.
Full explanation for 1 second ON 1 second OFF
A short pulse every 4 seconds

Your boiler is currently switched off but is monitoring the temperature to prevent the internal pipes from freezing.

Low DIY-safe £0

What to check first

  1. Turn the main control knob from the 'O' (Off) position to either 'Summer' or 'Winter' mode to restore normal heating and hot water.
Full explanation for A short pulse every 4 seconds
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
Lock-out signal lamp red

Your boiler is failing to detect a flame correctly during startup, causing it to stop for safety until you manually reset it.

High DIY-safe £120-£280

What to check first

  1. Check that your gas pre-payment meter (if applicable) has credit
  2. Ensure other gas appliances like your hob are working to confirm gas supply
  3. Press the reset button once to see if the fault was a temporary glitch

Parts commonly replaced

  • Ignition Electrode
  • Flame Sensing Electrode
  • Gas Valve
  • PCB
Full explanation for Lock-out signal lamp red