Baxi Suprima 50 Fault codes & diagnostics

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

Regular Natural Gas 14.7 kW 1997-2002 Discontinued
GC Number 41-607-77

Replaced by: Potterton Suprima HE

Download the Baxi Suprima 50 manual The official installation & service manual (PDF) — the exact document these fault codes were verified against. PDF

This boiler uses LED flash patterns

Count the flashes in one repeating group before the pause. That number is your fault code. Do not reset until you have noted it. How to read fault codes →

Severity at a glance

Each cell = one fault code. Hover to identify.
8 High 1 Medium 3 Low
Just want the most common Baxi Suprima 50 faults?
The top 6 problems in plain English — with causes, DIY checks and repair costs.
Fault codes

All 12 documented codes

Tap any card for details

LED / flash-pattern codes
1 red flash

Your boiler has likely overheated or a sensor has detected an incorrect temperature, causing the system to shut down for safety.

High DIY-safe £120-280

What to check first

  1. Wait for the boiler to cool down for 20 minutes
  2. Ensure all radiator valves are open to allow water to circulate
  3. Press the 'Reset' button on the front of the control panel

Parts commonly replaced

  • Thermistor/Temperature Sensor
  • Overheat Thermostat
  • Printed Circuit Board (PCB)

Related codes

Full explanation for 1 red flash
2 red flashes

Your boiler has switched itself off because it has become too hot internally and needs to cool down for safety.

High DIY-safe £90-250

What to check first

  1. Wait for the boiler to cool down for at least 20 minutes
  2. Ensure all radiator valves are open to allow water to circulate
  3. Press the 'Reset' button on the control panel to restart the boiler

Parts commonly replaced

  • Circulation pump
  • Overheat thermostat
  • Temperature sensor (NTC thermistor)

Related codes

Full explanation for 2 red flashes
3 green flashes

Your boiler is struggling to keep its burner lit and is trying to restart itself automatically.

Medium Engineer only £120-350

Parts commonly replaced

  • Flame Sensing Electrode
  • PCB (Control Board)
  • Gas Valve

Related codes

Full explanation for 3 green flashes
3 red flashes

Your boiler is failing to light its burner after five attempts, which means it cannot provide heat or hot water and has gone into lockout for safety.

High DIY-safe £120-350

What to check first

  1. Check if other gas appliances, like a cooker, are working to ensure gas is reaching the property
  2. Check if your prepayment gas meter has credit
  3. Press the 'Reset' button on the front of the boiler for five seconds

Parts commonly replaced

  • Ignition Electrode
  • Gas Valve
  • Printed Circuit Board (PCB)

Related codes

Full explanation for 3 red flashes
4 green flashes

Your boiler is having a temporary 'conversation' issue between its internal parts and should fix itself momentarily.

Low DIY-safe £0-120

What to check first

  1. Wait a few minutes for the boiler to automatically reset itself.
  2. If the flashing continues, turn the control knob to 'Reset' for 5 seconds and then back to your desired setting.
  3. Check that any external thermostats or timers are calling for heat.

Parts commonly replaced

  • None (usually self-correcting)
  • Printed Circuit Board (PCB)

Related codes

Full explanation for 4 green flashes
4 red flashes

Your boiler has detected that its internal fan is not spinning correctly, which means it cannot safely vent exhaust gases and has shut down as a precaution.

High Engineer only £180-350

Parts commonly replaced

  • Fan Assembly
  • Air Pressure Switch
  • PCB (Printed Circuit Board)

Related codes

Full explanation for 4 red flashes
5 green flashes

Your boiler has experienced a brief electronic 'hiccup' or data error and is trying to clear itself automatically.

Low DIY-safe £0-280

What to check first

  1. Wait for the boiler to self-reset as it is programmed to do.
  2. If the flashing continues for more than 10 minutes, turn the power off at the fused spur switch for 30 seconds and turn it back on.
  3. Press the reset button if the light pattern changes to a static red light.

Parts commonly replaced

  • None (usually self-corrects)
  • Printed Circuit Board (PCB)
Full explanation for 5 green flashes
5 red flashes

Your boiler's computer memory has developed a technical fault, causing the system to lock out for safety.

High Engineer only £180-350

Parts commonly replaced

  • Main PCB (Printed Circuit Board)
  • Parameter Storage Unit
Full explanation for 5 red flashes
6 green flashes

Your boiler has experienced a brief internal glitch and is currently attempting to restart itself automatically.

Low DIY-safe £0-120

What to check first

  1. Wait up to 10 minutes for the boiler to complete its self-reset process
  2. Monitor the control panel to see if the flashing light stops and returns to steady green
  3. If the flashing continues, turn the temperature control knob to 'Off' and back to the desired setting to trigger a manual reset

Parts commonly replaced

  • No parts usually required
  • PCB (if fault becomes permanent)
Full explanation for 6 green flashes
6 red flashes

Your boiler has detected an internal communication error and has shut down as a safety precaution.

High Engineer only £180-350

Parts commonly replaced

  • Main PCB (Printed Circuit Board)
  • Ignition Lead
  • Electrode Set
Full explanation for 6 red flashes
Digital codes
119

Your boiler has stopped working because the water pressure in the central heating system has dropped too low to operate safely.

High DIY-safe £0-120

What to check first

  1. Locate the external filling loop, which is a silver braided hose usually found underneath the boiler or near the hot water cylinder.
  2. Slowly open the one or two valves on the filling loop until you hear water flowing.
  3. Watch the pressure gauge and close the valves tightly once the needle reaches between 1 and 1.5 bar.

Parts commonly replaced

  • Filling loop
  • Expansion vessel
  • Pressure relief valve

Related codes

Full explanation for 119
125

Your boiler has stopped working because the water isn't moving through the system properly, which is causing it to overheat and shut down.

High DIY-safe £180-450

What to check first

  1. Check that your home's radiator valves are fully open
  2. Check that the central heating pump is not stuck by gently tapping it
  3. Bleed all radiators to remove trapped air that could be blocking water flow

Parts commonly replaced

  • Central heating pump
  • Overheat thermostat
  • Diverter valve

Related codes

Full explanation for 125
Status & diagnostic codes

1 operating states & engineer diagnostics

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

1 green flash Status Your boiler has reached its target temperature and is simply resting until it needs to heat up again.