How to Fix Vokera A03 Fault Code (Fan Fault) UK
Vokera A03 means fan fault. UK diagnosis, parts to order, reset sequence.
What A03 means
Vokera A03 indicates fan fault. The boiler will lock out and refuse to fire until the fault is cleared.
Do not simply reset — A03 is stored in the Vokera error log and will re-trigger within minutes if the underlying part has failed.
Diagnostic sequence
Enter service mode on the Vokera boiler and read the flow/return/DHW temperatures, fan PWM, ionisation current and pump speed.
Cross-reference against the Vokera technical manual — A03 typically points to two or three candidate parts.
- Check wiring harness continuity to the suspect sensor before condemning it.
- Isolate at the fused spur, discharge and re-inspect connectors.
- Measure resistance / voltage at the PCB plug per Vokera test procedure.
Parts to have on the van
Carry a set of NTC sensors, an ignition electrode kit and a fan for Vokera — these three parts clear >70% of A03 call-outs.
Recommission
After the fix, run the Vokera boiler through a full flow test, gas rate, and combustion analysis. Log to the Benchmark book to preserve manufacturer warranty.
Frequently asked questions
- Can I reset A03 without changing parts?
- Only if the fault has cleared (e.g. low pressure repressurised). Persistent A03 means a hardware failure.
- Which is the most common cause of Vokera A03?
- On Vokera boilers, A03 most often points to the sensor or actuator matching its meaning (fan fault); check wiring and connector integrity first.
- Is a Gas Safe engineer required?
- Yes — any works past the boiler case seal require a Gas Safe registered engineer under UK law.
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