Common problems guide

The most common Ferroli F24 problems

The faults most likely to send a Ferroli F24 into lockout — with plain-English causes, what to check first, estimated repair costs and whether you need a Gas Safe engineer.

This model is discontinued. Parts can be harder to source and expensive. If repair costs are mounting, a new A-rated boiler may be the smarter choice.
10 documented codes
6 most common
2 DIY-safe checks
4 engineer needed

The 6 most common faults

01
5 (Flashing Light) High DIY-safe

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

What to try first

Locate the external filling loop, which is usually a small metal braided hose with one or two valves located underneath the boiler.Open the valve(s) slowly to allow water into the system while watching the pressure gauge on the front of the boiler.Close the valve(s) tightly once the needle on the gauge reaches the green zone, typically between 1.0 and 1.5 bar.

Est. cost
£60-120
Parts
Filling loop, Pressure relief valve, Pressure sensor
Full guide for 5 (Flashing Light)
02
LED 5 bar (Flashing light) High DIY-safe

Your boiler has detected that there is not enough water inside your heating system to run safely and correctly.

What to try first

Locate the external filling loop (a flexible metal or braided pipe) underneath your boiler.Open the small valve handle on the filling loop to allow cold water into the system until the pressure gauge reads between 1.0 and 1.5 bar.Close the valve tightly to prevent over-pressurisation.

Est. cost
£80-120
Parts
Pressure relief valve, Expansion vessel, Pressure sensor
Full guide for LED 5 bar (Flashing light)
03
LED 2 High Engineer

Your boiler has detected an internal failure or lack of ignition, which has caused it to automatically stop working to ensure your safety.

Est. cost
£120-250
Parts
Ignition electrode, Gas valve, Printed Circuit Board (PCB)
Full guide for LED 2
04
LED 5 bar (Permanent light) High Engineer

Your boiler is failing to detect a stable electrical supply, which is preventing it from starting up or operating correctly.

Est. cost
£120-250
Parts
Printed Circuit Board (PCB), Wiring harness, Power supply fuse
Full guide for LED 5 bar (Permanent light)
05
Red lockout light High Engineer

Your boiler has stopped working for safety reasons and needs a manual reset or a professional check to get your heating and hot water back on.

Est. cost
£120-250
Parts
Ignition electrode, Flame sensor, Gas valve
Full guide for Red lockout light
06
4 (Flashing Light) Low Engineer

Your boiler is currently idle and is simply waiting for a signal to provide heating or hot water, so there is no fault with the unit.

Full guide for 4 (Flashing Light)
Parts most often replaced

on the Ferroli F24

Filling loopPressure relief valvePressure sensorExpansion vesselIgnition electrodeGas valve

Based on parts cited in our fault code database. Your engineer will confirm what's actually needed after diagnosis.

Call a Gas Safe engineer if…

  • You can smell gas or see signs of a leak
  • The Ferroli shows an Emergency or High severity code
  • The boiler keeps locking out after repeated resets
  • You've tried the DIY checks and the fault hasn't cleared
  • There's visible water leaking from the boiler
  • The flame is yellow or orange instead of blue
See the full 10-code list for the Ferroli F24

Related guides

Boiler losing pressure → No hot water → When to replace → Symptom checker →