Common problems guide

The most common Vokera boiler problems

The faults we see most often across the Vokera 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 61 Vokera boiler models.

476 unique codes
61 models covered
8 DIY-safe (top 8)
8 engineer needed

The most common Vokera faults

01
E020 High DIY-safe

Your boiler has shut down because it has reached an unsafe temperature, triggered by a safety sensor that prevents the unit from overheating.

Why it happens: This fault occurs when the water inside the boiler gets too hot, causing a safety switch to Cut off the system to prevent damage. The most common reasons are a pump failure that stops water from moving or a blockage in the heat exchanger that restricts flow.

What to try first

Check that all radiator valves are fully open to allow water to circulate.Ensure your system pressure is topped up to between 1 and 1.5 bar.Turn the boiler off and on again, or press the 'Reset' button to clear the lockout once the system has cooled down.

Est. cost
£120-280
Parts
Limit thermostat (Overheat sensor), Circulation pump, Main Heat Exchanger (Flushing)
Full guide for Evolve E020
02
E040 High DIY-safe

Your boiler has detected that the water pressure is either too low or the sensor that monitors it is not communicating correctly.

Why it happens: This fault occurs when the boiler's internal sensor detects that there isn't enough water pressure to safely heat your home, or if the sensor itself has developed an electrical fault. The most common reason is a gradual loss of water through a small leak or from bleeding your radiators, which drops the pressure below the required operational limit. When this happens, the boiler shuts down as a safety precaution to prevent the internal components from overheating.

What to try first

Locate the pressure gauge on the front of the boiler or via the digital screen.If the pressure is below 1 bar, use the filling loop underneath the boiler to carefully top it up to 1.5 bar.Restart the boiler to see if the error clears once the pressure is stable.

Est. cost
£90-180
Parts
Water pressure transducer, Filling loop valves
Full guide for Evolve E040
03
E041 High DIY-safe

Your boiler has detected that the water pressure is incorrect or the sensor that monitors it is not communicating properly.

Why it happens: This fault occurs when the boiler's internal sensor detects that there is not enough water pressure to operate safely. The most common reason is a slow leak somewhere in your central heating system or air being released from the radiators, which causes the pressure to drop below the required threshold. It can also be caused by the sensor itself becoming blocked with debris or failing electronically.

What to try first

Check the pressure gauge on the front of the boiler; it should be between 1 and 1.5 bar.If the pressure is too low, use the filling loop valves to top up the system until the gauge reaches 1.2 bar.Reset the boiler to see if the fault clears.

Est. cost
£120-210
Parts
Water pressure transducer, Filling loop valve
Full guide for Evolve E041
04
Green LED: Off | Red LED: On High DIY-safe

Your boiler has failed to light the gas flame and has shut down as a safety precaution.

Why it happens: This fault occurs when the boiler attempts to start up but cannot detect a sustained flame, leading it to shut down for your safety. The most common reasons include a lack of gas reaching the unit, worn-out spark electrodes that can no longer ignite the fuel, or a faulty sensor that fails to 'see' the flame even if it is lit.

What to try first

Check that your gas supply is turned on and other gas appliances are workingRotate the control knob to the 'OFF/RESET' position and then back to the 'ON' positionWait for the boiler to attempt to restart; if the red light remains, a professional is required

Est. cost
£90-£250
Parts
Ignition Electrode, Flame Sensing Probe, Gas Valve
Full guide for Aquanova Green LED: Off | Red LED: On
05
Fault light is on High DIY-safe

Your boiler has detected a general internal error and has locked itself out for safety, meaning your heating and hot water will not work until it is reset or repaired.

Why it happens: This fault occurs when the boiler's internal computer detects an inconsistency in the ignition process or a failure in one of its safety sensors. The most common reasons are that the boiler is struggling to generate a spark to light the gas, or a faulty sensor is sending incorrect temperature readings to the main control board.

What to try first

Check if your gas prepay meter has creditRotate the mode selector switch to the 'OFF/RESET' position, wait five seconds, then move it back to 'Auto' or 'Hot Water Only'Check your pressure gauge is between 1 and 1.5 bar; if it is too low, top it up using the filling loop

Est. cost
£100-350
Parts
Ignition Electrode, Printed Circuit Board (PCB), Thermistor (NTC Sensor)
Full guide for Compact HE Fault light is on
06
Red | On every 0.5 second High DIY-safe

Your boiler has entered a safety lockout mode due to a critical internal fault or an ignition failure.

Why it happens: This fault occurs when the boiler's control system detects a critical safety issue, most often failing to light the flame after several attempts. It can be caused by a lack of gas reaching the burner, a worn-out spark electrode, or an electrical failure within the main control board. Essentially, the boiler has stopped working to prevent unburnt gas from building up or to protect its internal components from damage.

What to try first

Move the mode selector switch to the 'OFF/RESET' position.Wait approximately 10 seconds.Move the switch back to either 'Hot Water Only' or 'Heating and Hot Water' and wait for the boiler to attempt to reignite.

Est. cost
£100-£350
Parts
Ignition electrode, Printed Circuit Board (PCB), Gas Valve
Full guide for Compact HE Red | On every 0.5 second
07
RED LED ON every 0.5-secs High DIY-safe

Your boiler has detected a safety-related issue with its internal components or airflow and has locked itself down to prevent damage.

Why it happens: This fault occurs when the boiler's safety sensors detect that the system cannot safely move air or water through the unit. It is most commonly caused by a mechanical failure in the fan or a blockage in the flue and condensate drainage system that prevents the boiler from 'breathing' correctly. In some cases, it can also be triggered if the unit overheats due to a lack of water circulation.

What to try first

Check that the system water pressure is between 1 and 1.5 bar on the pressure gaugeTurn the mode selector switch to 'OFF/RESET' for a few seconds, then back to the heater or hot water iconEnsure the external flue terminal is not obstructed by debris or garden growth

Est. cost
£100-350
Parts
Fan, Air Pressure Switch, Limit Thermostat
Full guide for Compact HE RED LED ON every 0.5-secs
08
RED LED Solid High DIY-safe

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

Why it happens: This fault occurs when the water inside the boiler exceeds a safe temperature, triggering a mechanical safety switch to cut off the burner. The most common reasons are a failed pump that isn't moving water efficiently, or a build-up of sludge and debris that is restricting flow through the heat exchanger.

What to try first

Check that your radiator valves are open to allow water to flow.Ensure the system pressure is between 1 and 1.5 bar on the pressure gauge.Wait for the boiler to cool down, then turn the mode selector switch to 'OFF/RESET' for a few seconds before switching it back to 'ON'.

Est. cost
£90-180
Parts
Overheat Limit Thermostat, Circulation Pump, Thermistor (NTC Sensor)
Full guide for Compact 29HE RED LED Solid

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