Vokèra Boiler Fault Codes Causes & Fixes

If your Vokèra boiler is showing a fault code, it can feel worrying, especially when heating or hot water suddenly stops. In reality, these codes are the boiler’s way of explaining what it has detected and why it has shut itself down.

They are safety messages first and foremost, designed to prevent damage and keep your home safe.

Below is a plain-English explanation of the most common Vokèra boiler fault codes to help you understand what is happening, what you can safely check yourself, and when it’s time to call in a professional.

How Vokèra boiler fault codes work

A Vokèra boiler constantly checks water pressure, temperatures, ignition, airflow, and combustion conditions.

If anything falls outside the safe range, the boiler locks out and displays a fault code. This protects key components such as the heat exchanger, burner, and flue system.

Different Vokèra models use different code formats. Many display “A” codes, Mynute models often use “AL” codes, and newer Evolve boilers use more detailed “E” codes. The meaning changes slightly by model, but the safety logic is always the same.

Vokèra “A” series fault codes

A01 / 01 – Ignition failure

This means the boiler has tried to light but cannot detect a flame. Sometimes this happens after a temporary gas interruption.

You can check that the gas supply is on and try a single reset. If A01 keeps returning, it usually points to an issue with the ignition system, gas valve, or burner and needs professional attention.

A02 / 02 – Overheat or limit thermostat fault

The boiler has become too hot and shut itself down. Let it cool fully, check that radiators have been bled, and make sure the pressure is correct before resetting once. If overheating happens again, there may be a circulation issue, pump fault, or blockage that needs investigation.

A11 – False flame detected

The boiler believes a flame is present when it should not be firing. This is a combustion-related safety issue and is not something you can resolve at home. An engineer will need to check flame sensing and controls.

A04 / 40 / 41 – Low water pressure

System pressure has dropped below the safe level. When cold, most Vokèra boilers operate best at around 1.2 to 1.5 bar. You can carefully top up using the filling loop and then reset. If pressure keeps falling, there is likely a leak or expansion vessel problem.

03 – Fan or flue fault

This code indicates the boiler cannot confirm safe airflow through the flue. Because this affects how exhaust gases leave the property, it must only be checked by a registered engineer.

A06 – Domestic hot water thermistor fault

The boiler is not getting a reliable temperature reading for hot water. This often causes fluctuating water temperature or poor hot water performance and usually means the sensor needs replacing.

A07 – Primary flow thermistor fault

The boiler is detecting an abnormal flow temperature. This can be linked to restricted circulation, limescale buildup, or a faulty sensor and should be investigated professionally.

A08 – Return thermistor fault

The return temperature reading is incorrect or too high. This can be caused by restricted water flow or a failing sensor.

A09 – Flue thermistor fault

A problem has been detected with flue gas temperature monitoring. Because this relates directly to fume safety, it always requires professional checks.

A77 – Low-temperature thermostat fault

The boiler has identified an issue with its internal low-temperature or frost protection thermostat. This is an internal control fault and needs an engineer to test or replace the component.

Vokèra boiler status and service messages

St – Autostop

The boiler has stopped automatically after detecting a safety condition.

CL – Call for service

This is the boiler’s way of saying it needs professional attention or servicing.

ADJ – Calibration mode

The boiler is in calibration mode, which should only ever be used by trained engineers.

ACO – Service operation

The boiler is in a dedicated service or testing mode.

N/A – Flame on

Confirms that the burner flame is currently present.

P or flashing P – Preheat active

The hot water preheat function is running.

Hours or standby or off

“Hours” means the boiler has power but is not firing, which usually means it is switched off.

Vokèra Mynute “AL” fault codes

AL10 / AL20 / AL21 / AL26 / AL28 / AL34 – General fault

These codes indicate a general internal fault. A reset may clear a one-off issue, but if the code comes back, further checks are required.

AL40 / AL41 – Low system pressure

The boiler has detected low water pressure. Topping up to around 1.5 bar may resolve it. Persistent pressure loss points to a system issue rather than the boiler itself.

AL52 / AL55 / AL60 / AL71 / AL73 / AL74 / AL79 – Internal fault

These relate to internal controls or components. They are not user-repairable and should be diagnosed by an engineer.

AL74 / AL79 – Persistent fault

If these return after a reset, it usually means the boiler has identified an ongoing issue that needs professional repair.

Vokèra Evolve fault codes

E10 – Flame lockout

The boiler failed to establish a stable flame. One reset is acceptable after checking the gas supply, but repeated lockouts require investigation.

E011 – Extraneous flame

A flame has been detected when the boiler should not be firing. This is a serious combustion safety issue.

E085 / E094 / E095 – Combustion or high carbon monoxide fault

Unsafe combustion conditions have been detected. Turn the boiler off, ventilate the area, and arrange an urgent engineer visit.

E020 – Overheat detected

The boiler has overheated. If this happens more than once, circulation or pump problems are likely.

E030 – Fan fault

The fan is not operating correctly. Because the fan controls safe removal of fumes, this must be checked professionally.

E040 / E041 – Water pressure transducer issue

The boiler is seeing incorrect pressure readings. Check actual system pressure first; if it is correct, the sensor may be faulty.

E042 – Water pressure transducer fault

A confirmed fault with the pressure sensor that normally requires replacement.

E060 – Hot water temperature probe fault

The boiler cannot read hot water temperature correctly, often causing unstable or no hot water.

4070 – Flow sensor over-temperature

The boiler has detected excessive temperature at the flow sensor, often due to poor circulation.

E077 – Main heating thermostat fault

The thermostat controlling the main heating circuit is not behaving as expected.

E080 – Return line probe fault

The return temperature sensor is reporting incorrect or unsafe readings.

E090 – Flue gas over-temperature

Flue gases are hotter than they should be. This can indicate a blocked heat exchanger or flue issue and needs urgent attention.

E091 – Clean primary heat exchanger

The boiler has detected reduced heat transfer efficiency and is requesting a professional clean.

Pressure out of range – Too low or too high

Low pressure can usually be topped up. High pressure often points to an expansion vessel or pressure relief valve problem.

Communication fault – Control board error

The boiler’s internal boards are not communicating correctly. This is an electrical or wiring issue that requires diagnosis.

E021 / E022 / E023 / E024 / E067 / E088 / E097 – Ionisation alarm

These codes relate to flame sensing and combustion stability and should be checked by an engineer.

E058 – Main voltage error

An electrical supply issue has been detected.

E065 – Current modulation alarm

The boiler has detected a problem with how electrical current is controlled during operation.

E086 – Fumes obstruction alarm

A possible blockage in the flue or exhaust path has been detected. Switch the boiler off and arrange an urgent inspection.

What you can check yourself and when to stop

You can safely check system pressure when the boiler is cold and top it up if needed. You can also try a single reset after a one-off fault. If a code keeps coming back, or if it involves combustion, fumes, fans, or overheating, it is important to stop and seek professional help.

For safety and peace of mind, always use a properly registered engineer. You can verify credentials through Gas Safe Register, which is the official gas safety authority in the UK.

Frequently asked questions about Vokèra boiler error codes

People often notice a Vokèra boiler error code appear and immediately worry that something major has gone wrong. In reality, many questions come up simply because boilers react to everyday changes in the home, the weather, or the way the heating system is used.

The answers below cover common concerns that are not always explained in manuals but are very relevant if you are dealing with Vokèra boiler fault codes.

Can cold weather or winter conditions trigger Vokèra error codes?

Yes, they can. During colder weather, it is normal for system pressure to dip slightly as water contracts, which can sometimes trigger a low-pressure warning.

Freezing temperatures can also affect external pipework, particularly condensate pipes, causing the boiler to shut down as a safety measure. These issues often show up during cold snaps rather than because of a fault developing inside the boiler itself.

Do Vokèra boiler error codes ever clear on their own?

Some do. If a Vokèra boiler temporarily overheats or detects a short-term issue, it may return to normal once conditions stabilise, such as after cooling down.

Other codes will stay on the display until the boiler is manually reset or the underlying problem is fixed. If the same code keeps returning, it is usually the boiler telling you that something still needs attention.

Can a power cut or electrical issue cause a Vokèra fault code?

Yes. After a power cut or electrical interruption, a Vokèra boiler may display a fault code or fail to restart straight away. In many cases, turning the boiler off at the fused spur for a short time and then switching it back on is enough to restore normal operation. If electrical-related codes appear regularly, it may point to a deeper wiring or control issue.

Is it safe to leave a Vokèra boiler showing an error code?

It depends on the code, but in general it is not a good idea to ignore it. Some error codes simply stop heating or hot water, while others relate to safety systems such as overheating or combustion monitoring. If the boiler does not return to normal after basic checks and one reset, arranging an engineer visit is the safest option.

Can low water pressure cause long-term problems if I keep topping up?

Yes, it can. Repeatedly topping up the pressure without fixing the cause can put extra strain on the system.

Over time, this can lead to corrosion, pump wear, or damage to internal components. If your Vokèra boiler frequently shows low-pressure codes, it is usually a sign that there is a leak or an expansion vessel issue that needs proper repair.

Will my Vokèra boiler still work while an error code is showing?

In most cases, no. When a genuine error code appears, the boiler has usually shut down to protect itself.

This means heating and hot water will not operate until the issue is resolved. Some display messages are simply status updates, but true fault codes normally stop the boiler from running.

Does regular servicing really help prevent error codes?

Absolutely. A routine service allows an engineer to clean components, check combustion, test sensors, and spot early signs of blockages or wear.

Many of the error codes people experience could be avoided or delayed with regular servicing, as small issues are dealt with before they trigger a shutdown.

Can air in radiators or pipework cause error codes?

Yes, trapped air can cause circulation problems, which may lead to overheating or temperature-related fault codes. Bleeding radiators and keeping the system pressure within the correct range helps the boiler circulate water properly and reduces the risk of these issues.

Are Vokèra error codes the same on every model?

Not always. While many codes are similar across the range, different Vokèra models can display faults differently.

Older boilers, Mynute models, and newer Evolve boilers all use slightly different code formats. This is why the same problem may appear under a different code depending on the boiler.

Is it okay to keep resetting a Vokèra boiler when a fault appears?

A single reset after basic checks is usually fine. Repeatedly resetting the boiler, however, can hide a serious problem and potentially make it worse. If you find yourself resetting your Vokèra boiler often, it is a strong sign that a professional check is needed.

If you are ever unsure about a fault code or what it means for safety, the best course of action is to stop and seek advice from a properly registered professional. You can also verify engineer credentials through Gas Safe Register, which is the official body responsible for gas safety in the UK.