Common problems guide

The most common Saunier Duval Ecosy 24E problems

The faults most likely to send a Saunier Duval Ecosy 24E 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.
40 documented codes
6 most common
1 DIY-safe checks
5 engineer needed

The 6 most common faults

01
1 2 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 filling loop (typically a silver braided hose with one or two valves underneath the boiler).Slowly open the valve(s) to allow cold mains water into the system until the pressure gauge reads between 1.0 and 1.5 bar.Close the valve(s) tightly to stop the flow and ensure no water is leaking.

Est. cost
£0-£120
Parts
Filling loop, Pressure relief valve, Pressure sensor
Full guide for 1 2
02
1 8 High Engineer

Your boiler has detected that the water inside the unit is dangerously overheated, so it has safely shut itself down to prevent damage.

Est. cost
£150-250
Parts
NTC Temperature Sensor, Pump, Primary Heat Exchanger
Full guide for 1 8
03
1 9 High Engineer

Your boiler has shut down because it thinks the water returning to the system is dangerously hot, which could indicate a flow blockage or a faulty sensor.

Est. cost
£120-250
Parts
NTC Return Thermistor, Central Heating Pump, Primary Heat Exchanger
Full guide for 1 9
04
9 25 blinking High Engineer

Your boiler has stopped working because it cannot move the hot water around your system effectively, so it has shut down to protect itself.

Est. cost
£150-300
Parts
Central heating pump, Flow sensor, Printed Circuit Board
Full guide for 9 25 blinking
05
02 High Engineer

Your boiler is failing to ignite because it cannot detect a flame, which is often caused by air trapped in the gas supply.

Est. cost
£120-£250
Parts
Ignition electrode, Gas valve, PCB
Full guide for 02
06
03. High Engineer

Your boiler's main internal computer has developed a malfunction and can no longer control the heating process safely.

Est. cost
£250-£450
Parts
Automatic Control Module, Printed Circuit Board (PCB)
Full guide for 03.
Parts most often replaced

on the Saunier Duval Ecosy 24E

Filling loopPressure relief valvePressure sensorNTC Temperature SensorPumpPrimary Heat Exchanger

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 Saunier Duval 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 40-code list for the Saunier Duval Ecosy 24E

Related guides

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