BoilerFaultCodesThe 6 most common faults
01
E01 High DIY-safe
Your boiler has stopped running because it failed to light, likely due to a problem with the oil supply or a burner fault.
What to try first
Check that your heating oil tank actually has fuel in itEnsure the oil supply valve from the tank is fully openPress the illuminated reset button on the front of the burner once
02
E04 High DIY-safe
Your boiler has detected that there is not enough water pressure in the pipes to operate safely.
What to try first
Check the pressure gauge on the boiler or expansion vessel; it should be between 1.0 and 1.5 bar.Locate the external filling loop and slowly open the valves to top up the system with water until the gauge reaches 1.2 bar.Ensure both valves on the filling loop are closed tightly and reset the boiler.
03
E02 High Engineer
Your boiler has switched itself off because it has reached an unsafe temperature to prevent internal damage.
Full guide for E0204
E05 High Engineer
Your boiler has lost its ability to monitor the temperature of the water leaving the unit, meaning it cannot operate safely and has shut down.
Full guide for E0505
E06 High Engineer
Your boiler has detected a problem with the sensor that monitors the temperature of your hot water, meaning it cannot safely provide hot water to your taps.
Full guide for E0606
E12 High Engineer
Your boiler's hot water temperature sensor has developed a fault or become disconnected, meaning the system can no longer monitor the water temperature accurately.
Full guide for E12on the Warmflow Agentis Boilerhouse
Oil nozzleOil pumpPhotocellFuel filterFilling loopExpansion vessel
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 Warmflow 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
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