Common problems guide

The most common Warmflow boiler problems

The faults we see most often across the Warmflow range — with plain-English causes, what to check first, estimated repair costs, and whether it's a DIY job or needs a Gas Safe engineer. Based on fault-code data across 6 Warmflow boiler models.

15 unique codes
6 models covered
3 DIY-safe (top 8)
8 engineer needed

The most common Warmflow faults

01
E01 High DIY-safe

Your boiler's burner has stopped working because it cannot light the fuel, meaning your heating and hot water have turned off for safety.

What to try first

Check that your heating oil tank has enough fuelEnsure the oil supply valve is fully openPress the illuminated reset button on the burner once to try and restart the system

Est. cost
£120-350
Parts
Oil nozzle, Oil pump, Photocell
Full guide for Agentis Internal E01
02
E04 High DIY-safe

Your boiler has detected that there is not enough water pressure in the system to operate safely, which is often caused by a small leak or after bleeding your radiators.

What to try first

Locate the pressure gauge on the front of the boiler or under the casing.Check if the needle is below 1 bar (usually in the red zone).Use the external filling loop to top up the water pressure until the gauge reads between 1 and 1.5 bar.

Est. cost
£0-160
Parts
Filling loop valve, Expansion vessel, Auto air vent
Full guide for Agentis Internal E04
03
Burner control box lockout light lit High DIY-safe

Your boiler's burner has shut itself down for safety because it failed to light or maintain a flame.

What to try first

Check that you have plenty of oil in your storage tankEnsure the oil supply valves are fully openFirmly press the illuminated reset button on the burner once to restart

Est. cost
£120-280
Parts
Oil nozzle, Photocell, Oil pump
Full guide for Kabin Pak and Utility Burner control box lockout light lit
04
E02 High Engineer

Your boiler has overheated, causing a safety switch to trigger and shut down the system to prevent damage.

Est. cost
£120-350
Parts
Circulation pump, Overheat thermostat, Main heat exchanger cleaning
Full guide for Agentis Internal E02
05
E05 High Engineer

Your boiler has lost its ability to monitor the temperature of the water leaving the unit, meaning it cannot operate safely to provide heating or hot water.

Est. cost
£90-160
Parts
Flow NTC Temperature Sensor, Sensor Wiring Harness
Full guide for Agentis Internal E05
06
E06 High Engineer

Your boiler's hot water sensor has stopped working correctly, which means the system cannot safely monitor the temperature of the water going to your taps.

Est. cost
£90-160
Parts
DHW Flow NTC Sensor, Wiring harness
Full guide for Agentis Internal E06
07
E12 High Engineer

Your boiler has lost communication with its hot water temperature sensor, meaning it cannot safely monitor or heat your water tank.

Est. cost
£120-£210
Parts
Tank Control NTC Sensor, Sensor Wiring Harness
Full guide for Agentis Internal E12
08
E22 High Engineer

Your boiler's internal computer brain has suffered a memory error and can no longer process instructions safely.

Est. cost
£250-£450
Parts
Main PCB (Printed Circuit Board), Control Interface
Full guide for Agentis Internal E22

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