Vokera Boiler Problems, Fault Codes & How to Fix Them in 2026
Quick Answer: Vokera boiler problems are most commonly indicated by a flashing or solid red light on the control panel, accompanied by a fault code on the display. Common causes include ignition failure, overheating, low water pressure, fan faults, and thermistor problems. Some faults can be resolved by checking the system pressure or resetting the boiler — others always require a Gas Safe registered engineer.
A Vokera boiler breaking down leaves you without heating or hot water at the worst possible time. Understanding what the lights and fault codes on your boiler are telling you is the fastest route to identifying whether you can resolve the problem yourself or whether you need to call an engineer.
This guide covers every common Vokera boiler problem, all fault codes across the main model ranges, what each code means, and the clearest course of action for each fault in 2026.
Key Facts: Vokera Boiler Problem Relationships
- Vokera is a UK and Ireland boiler brand founded over 35 years ago, with its parent company Riello Group established in 1922 as a global supplier of heating appliances.
- A red flashing light on a Vokera boiler indicates that the boiler has detected a fault and entered lockout, preventing it from producing heating or hot water until the fault is resolved.
- A constant green light on a Vokera boiler confirms that the burner flame is active and the boiler is operating normally.
- A boiler lockout is a safety shutdown triggered by the Vokera boiler’s control board when it detects a fault it cannot safely continue operating through.
- A Gas Safe registered engineer is the only qualified professional legally permitted to diagnose and repair gas boiler faults in the UK, and most Vokera fault codes require one.
- The A01 fault code on a Vokera boiler indicates ignition failure where the flame has not been detected, and represents one of the most common Vokera faults.
- The A04 fault code on a Vokera boiler indicates insufficient system water pressure, which can sometimes be resolved by the homeowner repressurising the system.
- The A03 fault code on a Vokera boiler indicates a fan fault, meaning the component responsible for expelling combustion gases is not functioning correctly.
- The A02 fault code on a Vokera boiler indicates a limit thermostat fault, typically associated with the boiler overheating.
- An AL40 fault code on a Vokera Mynute boiler indicates low system pressure and should be addressed by checking and refilling the system before resetting the boiler.
- An E030 fault code on a Vokera Evolve Combi or Evolve System boiler indicates a fan fault requiring professional attention.
- Annual boiler servicing is the most effective way to prevent recurring Vokera fault codes and should be carried out by a Gas Safe registered engineer every year.
What Does the Red Flashing Light on a Vokera Boiler Mean?
The indicator lights on a Vokera boiler provide the first level of diagnostic information before you even look at a fault code. Understanding what each light pattern means narrows down the problem quickly.
A constant green light with no red light present confirms that the boiler is working correctly and the burner flame is active. This is the normal operating state.
When the green light goes off and a constant red light appears, the boiler has entered a full lockout. This indicates one of three likely causes: the boiler is overheating, the pump is not circulating water correctly through the central heating system or to the hot water outlets, or the fan has failed and is not expelling combustion gases safely through the flue.
When both the green and red lights are on simultaneously, the boiler has detected a different category of fault. This combination typically indicates that the boiler has been left in service mode after a recent service, that the system water pressure is either too high or too low, or that one of the heating temperature sensors has developed a fault.
A flashing green light — without any red light — usually indicates that the boiler is on standby or that the hot water sensor is not functioning correctly. In this state, checking the thermostat settings and controls is a sensible first step before assuming a more serious fault.
How to Reset a Vokera Boiler
A reset will clear an active fault state and instruct the boiler to attempt a fresh start. It will resolve the fault permanently only if the underlying cause has already been addressed — if it has not, the fault code will reappear shortly after the reset.
To reset a Vokera boiler, move the mode selector switch to the OFF/RESET position and hold it there briefly. Then move the switch back to the desired operating mode — either hot water only or heating and hot water. If the boiler restarts successfully, the indicator light will return to a steady green. If the fault persists, the red light will reappear and a Gas Safe engineer should be contacted rather than attempting further resets.
Vokera Boiler Fault Codes: Full Reference Guide
Standard Vokera Boiler Fault Codes
| Fault Code | Meaning | Action Required |
|---|---|---|
| _St | Autostop | Check controls and settings |
| _CL | Call for service | Arrange annual service |
| A01 | Ignition failure — flame not detected | Call a Gas Safe engineer |
| A02 | Limit thermostat fault (overheating) | Call a Gas Safe engineer |
| A03 | Fan fault | Call a Gas Safe engineer |
| A04 | Insufficient system water pressure | Check and repressurise — call engineer if fault persists |
| A06 | Domestic hot water thermistor fault | Call a Gas Safe engineer |
| A07 | Primary flow thermistor fault — water temperature too high | Call a Gas Safe engineer |
| A08 | Return thermistor fault — water temperature too high | Call a Gas Safe engineer |
| A09 | Flue thermistor or flue thermistor counter fault | Call a Gas Safe engineer |
| A11 | False flame detected | Call a Gas Safe engineer |
| A77 | Low temperature thermostat fault | Call a Gas Safe engineer |
| ADJ | Calibration mode | Engineer action required |
| ACO | Service operation mode | Engineer action required |
| N/A | Flame active | Normal operation indicator |
Additional Standard Display Codes
| Code | Meaning |
|---|---|
| P | Preheating function active |
| P (blinking) | Preheating function running |
| Hours | Standby mode |
| — | Off |
| 01 | Failure to ignite |
| 02 | Overheating |
| 03 | Problem with fan or flue |
| 04 | Insufficient water pressure |
| 05 | Reset as for code 01 |
| 06 | Hot water thermistor open circuit |
| 07 | Primary thermistor open circuit |
Vokera Mynute Boiler Fault Codes
| Fault Code | Meaning | Action Required |
|---|---|---|
| AL10, AL20, AL21, AL26, AL28, AL34 | Various internal faults | Reset boiler — call engineer if fault reoccurs |
| AL40 | Low system water pressure | Check and refill system pressure — reset boiler — call engineer if fault reoccurs |
| AL41 | System pressure fault | Check and refill system pressure — call engineer if fault reoccurs |
| AL52, AL55, AL60, AL71, AL73, AL74, AL79 | Various faults requiring professional diagnosis | Call a Gas Safe engineer |
| AL74, AL79 | Faults with reset option | Reset boiler — call engineer if fault reoccurs |
Vokera Evolve Combi and Evolve System Fault Codes
| Fault Code | Meaning | Action Required |
|---|---|---|
| E10 | Flame lockout | Call a Gas Safe engineer |
| E011 | Extraneous flame detected | Call a Gas Safe engineer |
| E020 | Limit thermostat fault | Call a Gas Safe engineer |
| E030 | Fan fault | Call a Gas Safe engineer |
| E040 | Water transducer — check system water pressure | Check system pressure |
| E041 | Water transducer — check system water pressure | Check system pressure |
| E042 | Water transducer fault | Call a Gas Safe engineer |
| E060 | Domestic hot water probe fault | Call a Gas Safe engineer |
| E070 | Flow sensor over temperature fault | Call a Gas Safe engineer |
| E077 | Main zone water thermostat fault | Call a Gas Safe engineer |
| E080 | Return line probe fault — over temperature | Call a Gas Safe engineer |
| E090 | Flue gases over temperature | Call a Gas Safe engineer |
| E091 | Clean primary heat exchanger | Arrange service — call engineer |
| E021, E022, E023, E024, E067, E088, E097 | Ionisation alarm | Call a Gas Safe engineer |
| E085, E094, E095 | Combustion fault or high CO | Call a Gas Safe engineer immediately |
| E058 | Main voltage error | Call a Gas Safe engineer |
| E065 | Current modulation alarm | Call a Gas Safe engineer |
| E086 | Obstruction in flue gases path | Check external flue — call engineer |
| — | Water pressure low | Repressurise system |
| — | Water pressure high | Call a Gas Safe engineer |
| — | Boiler board communication lost | Call a Gas Safe engineer |
| — | BUS 485 communication lost | Call a Gas Safe engineer |
Common Vokera Boiler Problems Explained
Ignition Failure — A01, Code 01, E10
Ignition failure is one of the most common faults across the Vokera range. The boiler has attempted to light the burner and has not been able to detect a flame. This can be caused by a faulty ignition electrode, a failed flame sensor, a problem with the gas supply, or a PCB fault.
A Gas Safe engineer will test each component in the ignition sequence to identify which has failed. Checking that other gas appliances in the property are working normally before calling an engineer is a useful first step, as it can confirm whether the issue is specific to the boiler or related to the wider gas supply.
Overheating — A02, Code 02, E020
An overheating fault indicates that the boiler has detected water temperature exceeding safe limits and has shut down to prevent damage. Common causes include a blocked or partially closed valve restricting water flow, a failing pump that is not circulating water effectively, or a build-up of limescale on the heat exchanger creating localised hot spots.
This fault always requires a Gas Safe engineer. The engineer will identify the root cause of the overheating and carry out the appropriate repair before resetting the boiler.
Fan Fault — A03, Code 03, E030
The fan is responsible for drawing combustion air into the boiler and expelling waste gases safely through the flue. If the fan fails, stops, or is obstructed, the boiler cannot operate safely and will shut down. A failed fan motor, a blocked fan housing, or a wiring fault to the fan can all trigger this code.
A Gas Safe engineer must diagnose and repair or replace the fan. This is not a fault that can be investigated or resolved without the correct qualifications.
Low Water Pressure — A04, Code 04, AL40, AL41, E040, E041
Low system water pressure is one of the few Vokera faults that homeowners can address themselves before calling an engineer. If the pressure gauge on the boiler reads below 1 bar, the system needs to be repressurised using the filling loop.
Locate the filling loop — a short metal hose connecting the mains water supply to the central heating circuit — and open the valves at each end to allow water into the system. Watch the pressure gauge and close both valves as soon as the reading reaches 1 to 1.5 bar. Reset the boiler and confirm that the fault code clears.
If the pressure drops again shortly after repressurising, a leak somewhere in the system is the likely cause and a Gas Safe engineer will need to locate and repair it.
Thermistor Faults — A06, A07, A08, A09, E060, E070, E080, E090
Thermistors are temperature sensors that monitor the water and flue gas temperatures at different points in the boiler circuit. When a thermistor develops a fault — either through physical damage, a wiring issue, or the component simply wearing out — the boiler receives incorrect temperature readings and shuts down as a precaution.
All thermistor faults require a Gas Safe engineer to diagnose and replace the affected sensor. The specific code displayed will indicate which thermistor has failed, helping the engineer attend prepared with the correct replacement part.
Combustion Faults and High CO — E085, E094, E095
The E085, E094, and E095 fault codes on the Vokera Evolve range indicate a combustion problem or elevated carbon monoxide levels. These codes should be treated as urgent. If any of these codes appear, switch off the boiler immediately, ensure the property is ventilated, and call a Gas Safe engineer without delay. Do not reset the boiler or attempt to continue using it until the cause has been identified and resolved.
False Flame — A11, E011
A false flame code indicates that the boiler’s flame sensor is detecting a flame when the burner has not been instructed to fire, or is detecting an erroneous signal. This is typically caused by a faulty flame sensor or a PCB fault and requires a Gas Safe engineer to diagnose and repair.
How to Keep Your Vokera Boiler Running Reliably
The most effective way to prevent recurring fault codes on a Vokera boiler is consistent annual servicing. A Gas Safe engineer will clean internal components, check for early signs of wear, test the ignition and safety systems, and verify that the flue is clear — catching developing faults before they trigger a lockout.
An annual service also maintains the validity of the boiler warranty, where applicable. Skipping a service not only increases the risk of a breakdown but can also void warranty cover, leaving the homeowner responsible for the full cost of any subsequent repair.
If the boiler is no longer under warranty and has developed repeated faults, a boiler cover plan provides financial protection against the cost of unexpected breakdowns and typically includes the annual service cost within its terms.
Frequently Asked Questions
What does the red light on a Vokera boiler mean?
A constant red light on a Vokera boiler with the green light off indicates that the boiler has entered a full lockout. The most common causes are overheating, a pump failure preventing proper water circulation, or a fan fault preventing combustion gases from being safely expelled. If both the green and red lights are on simultaneously, the boiler may have been left in service mode, or the system pressure or a temperature sensor may be at fault. A Gas Safe engineer should be called if a reset does not resolve the issue.
How do I reset a Vokera boiler?
To reset a Vokera boiler, move the mode selector switch to the OFF/RESET position and hold it briefly, then move it back to the desired operating mode — hot water only or heating and hot water. If the boiler restarts successfully, the green light will remain steady. If the fault code reappears after the reset, do not attempt further resets — call a Gas Safe registered engineer to diagnose the underlying cause.
What does the Vokera A01 fault code mean?
The A01 fault code on a Vokera boiler indicates ignition failure — the boiler has attempted to light the burner but has been unable to detect a flame. This can be caused by a faulty ignition electrode, a failed flame sensor, an insufficient gas supply, or a PCB fault. A Gas Safe engineer must attend to test each component and identify which has failed. Before calling an engineer, confirm that other gas appliances in the property are working normally to rule out a wider gas supply issue.
What does the Vokera A04 fault code mean?
The A04 fault code on a Vokera boiler indicates insufficient system water pressure. The boiler requires a pressure of between 1 and 1.5 bar to operate correctly. If the pressure gauge reads below 1 bar, repressurise the system using the filling loop until the correct pressure is restored, then reset the boiler. If the pressure drops again after repressurising, a system leak is the likely cause and a Gas Safe engineer will need to locate and repair it.
Are Vokera boiler fault codes covered by warranty?
If your Vokera boiler is within its manufacturer warranty period and develops a fault covered by the warranty terms, the cost of parts and labour for the repair should be covered. To keep the warranty valid, the boiler must be serviced annually by a Gas Safe registered engineer and the installation must have been carried out correctly in the first instance. Check the specific warranty terms for your Vokera model and contact Vokera directly if you believe a fault may be covered before arranging an independent repair.
What does the Vokera E085 fault code mean?
The E085 fault code on a Vokera Evolve boiler indicates a combustion fault or elevated carbon monoxide levels. This is a serious fault that should be treated with urgency. Switch off the boiler, ventilate the property, and call a Gas Safe engineer immediately. Do not reset the boiler or attempt to continue using it. The same response applies to the related E094 and E095 codes, which also indicate combustion problems or high CO.
How often should a Vokera boiler be serviced?
A Vokera boiler should be serviced every year by a Gas Safe registered engineer. Annual servicing keeps the boiler operating efficiently, identifies developing faults before they cause a breakdown, and maintains the validity of the manufacturer warranty. Skipping an annual service increases the risk of unexpected faults and can void warranty cover, leaving the homeowner responsible for the full cost of any repairs that follow.
Should I replace my Vokera boiler if it keeps showing fault codes?
If a Vokera boiler is regularly displaying fault codes despite annual servicing and timely repairs, and is more than ten years old, the cumulative cost of ongoing repairs may begin to approach the cost of a new installation. A new boiler will carry a full manufacturer warranty, operate more efficiently, and is significantly less likely to develop recurring faults in the near term. A Gas Safe engineer can give you an honest assessment of whether your specific boiler is worth continuing to repair or whether replacement represents better long-term value.
Conclusion
Vokera boilers are reliable and well-built, but like any heating appliance they develop faults over time. Understanding what the indicator lights and fault codes are telling you is the first step towards resolving any problem quickly and at the lowest possible cost.
A small number of faults — particularly low water pressure indicated by the A04, AL40, or E040 codes — can be resolved at home by repressurising the system. For everything else, a Gas Safe registered engineer is the right call. Combustion faults such as E085, E094, and E095 should always be treated as urgent and the boiler switched off immediately.
Annual servicing remains the most reliable way to prevent fault codes from appearing in the first place, keep the boiler operating efficiently, and ensure that the manufacturer warranty remains valid throughout its term.
