Biasi Gaia Fault codes & diagnostics

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

Combi Natural GasLPG 24-28 kW 2000-2008 Discontinued

Replaced by: Riva Advance

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Severity at a glance

Each cell = one fault code. Hover to identify.
1 Emergency 5 High
Just want the most common Biasi Gaia faults?
The top 6 problems in plain English — with causes, DIY checks and repair costs.
Fault codes

All 6 documented codes

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Boiler ON (green) light off

Your boiler has lost power completely, meaning it will not turn on or provide any heating or hot water.

High DIY-safe £90-250

What to check first

  1. Check if other appliances in your home have power
  2. Check your main property fuse box to see if a circuit has tripped
  3. Ensure the boiler's power switch on the wall (fused spur) is turned on

Parts commonly replaced

  • Internal F1 or F2 glass fuses
  • Main Control PCB
  • External Fused Spur
Full explanation for Boiler ON (green) light off
Lock lamp / lock state

Your boiler has entered a safety lockout mode and stopped working because it failed to light or stay lit through several attempts.

High DIY-safe £100-280

What to check first

  1. Check that your gas supply is active and other gas appliances are working
  2. Locate the reset button or selector switch on the control panel
  3. Turn the selector to the 'R' (Reset) position for 2 seconds and then back to the on position

Parts commonly replaced

  • Ignition electrode
  • Flame sensing electrode
  • Gas valve
  • Pcb
Full explanation for Lock lamp / lock state
Lock state cause

Your boiler has switched itself off because it has reached an unsafe temperature, likely due to a blockage or a failure in how the water is moving through the system.

High DIY-safe £120-280

What to check first

  1. Check that all radiator valves are fully open
  2. Ensure the boiler pressure is between 1 and 1.5 bar on the gauge
  3. Try to reset the boiler once it has cooled down for 30 minutes

Parts commonly replaced

  • Safety Thermostat (Overheat Stat)
  • Circulation Pump
  • Main Heat Exchanger
  • Thermistor (NTC Sensor)
Full explanation for Lock state cause
Lockout lamp (red) on

Your boiler is trying to light but cannot successfully create or detect a flame, causing it to shut down for safety.

High DIY-safe £120-£350

What to check first

  1. Check that your gas supply is turned on at the meter
  2. Check if other gas appliances (like a hob) are working
  3. Press the reset button to attempt a restart

Parts commonly replaced

  • Ignition electrode
  • Flame detection probe
  • Gas valve
  • PCB
Full explanation for Lockout lamp (red) on
Main circuit pressure - red

Your boiler has too much water inside it, causing the pressure to rise to an unsafe level.

Emergency DIY-safe £100-250

What to check first

  1. Check that the filling loop valves under the boiler are tightly closed.
  2. Locate a radiator and use a bleed key to release water into a container until the pressure gauge falls to 1.5 bar.
  3. If the pressure continues to rise on its own, turn off the cold water mains and call a professional.

Parts commonly replaced

  • Filling loop valve
  • Expansion vessel
  • Pressure relief valve
Full explanation for Main circuit pressure - red
Main circuit pressure - yellow

Your boiler has detected that the water pressure is too low, which prevents it from heating up safely.

High DIY-safe £0-120

What to check first

  1. Locate the filling loop (usually a silver flexible hose) underneath or near the boiler.
  2. Slowly open the small valves on the filling loop until you hear water moving.
  3. Watch the pressure gauge and close the valves once the needle reaches between 1 and 1.5 bar.

Parts commonly replaced

  • Filling loop valves
  • Pressure sensor
  • Expansion vessel

Related codes

Full explanation for Main circuit pressure - yellow