Vokèra A03 fault codewhat it means and how to fix it
The appliance cannot confirm the fan is running correctly, so it will not permit the burner to light. This needs an engineer.
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What A03 means
The fan clears combustion products out through the flue, and no condensing appliance will open its gas valve until it has proved the fan is turning at the commanded speed. A03 means that proof failed. The interlock is absolute: there is no way to run the appliance around it, and there should not be. In service the two realistic causes are a fan that has worn out and a flue that is obstructed, and they are worth separating because they cost very different amounts. Fan bearings dry out after roughly eight to twelve years and usually give warning first, as a rumble or grind on start-up that the household gradually stops hearing. A flue obstruction — a nest, leaf litter, or render forced into the terminal during building work — changes the resistance the fan is working against, which throws the speed reading even though the fan itself is perfectly healthy. Replacing a good fan because nobody checked the flue is a common and avoidable expense.
What causes it
| Cause | What is actually happening | How likely |
|---|---|---|
| Fan bearings worn | The dominant cause on appliances beyond about eight years. Usually preceded by months of increasing noise on start-up. | Common |
| Flue blocked or obstructed | Nesting birds, debris, or building materials in the terminal. Changes fan loading enough to fail the speed check. | Occasional |
| Fan wiring or connector fault | The fan turns but the speed signal never reaches the board. Cheap if that is genuinely the whole problem. | Occasional |
| Control board misreading the signal | Diagnosed last, after the fan and the flue have both been ruled out properly. | Rare |
Can you fix it yourself?
Stop — this needs an engineer
What it costs to fix
Typical repair cost
£180–£420
A fan assembly is typically £280 to £420 fitted. A flue clearance or a connector repair is a call-out charge of £80 to £140.
Typical UK prices including parts and labour, updated August 2026. Your quote may differ.
What other owners found
Nobody has shared what worked for them on this code yet. If you have had it, you would be the first — and it genuinely helps the next person.
Related Vokèra fault codes
- A09Get it checkedThe flue gas sensor has recorded a temperature above the safe limit, or the sensor itself has failed. Either way the appliance stops.Related: fan and flue
- C6 224Get it checkedThe fan is not reaching the speed the boiler asked for, so combustion cannot be confirmed as safe and the burner has been prevented from firing.Related: fan and flue
- E16Get it checkedThe control board cannot confirm the fan is running at the speed it asked for, so it will not let the burner light. This one needs an engineer.Related: fan and flue
- F.32Get it checkedThe fan is not running at the speed the boiler expects, so combustion cannot be verified as safe and the boiler has locked out.Related: fan and flue
- E160Get it checkedThe fan is not running at the speed the appliance expects. Baxi direct engineers to check the fan and its cable, in that order.Related: fan and flue
- F3Get it checkedThe fan is not running at the speed the boiler expects, so it cannot confirm the flue is clearing and has stopped the burner firing.Related: fan and flue
Related guides
Common questions about Vokèra A03
Can I check anything myself before booking someone?
Look at the flue terminal from the ground in daylight and note whether there is anything obviously in it. That observation is genuinely useful. Do not reach into it, and do not remove the appliance casing.
The boiler has been noisy for months. Is that connected?
Almost certainly. A fan that grumbles on start-up and then quietens as it comes up to speed is a bearing on its way out, and this code is the end of that process.
Vokèra also lists A05 as a fan fault. What is the difference?
A03 generally means the fan is not running or not being detected at all; A05 means it is running but at the wrong speed. The diagnostic route is much the same and both need an engineer.
Sources and how we verified this
We establish the facts from the sources below and then write the explanation ourselves. We do not copy manufacturer wording and we do not host their manuals.
- Manufacturer technical and service documentation
- Interviews with working engineers
Checked by Technical reviewer (Gas Safe registration to be displayed on appointment) on 5 August 2026.