How to Fix Ariston 501 Fault Code (No Flame Detected) UK
Ariston 501 means no flame detected. UK diagnosis, parts to order, reset sequence.
What 501 means
Ariston 501 indicates no flame detected. The boiler will lock out and refuse to fire until the fault is cleared.
Do not simply reset — 501 is stored in the Ariston error log and will re-trigger within minutes if the underlying part has failed.
Diagnostic sequence
Enter service mode on the Ariston boiler and read the flow/return/DHW temperatures, fan PWM, ionisation current and pump speed.
Cross-reference against the Ariston technical manual — 501 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 Ariston test procedure.
Parts to have on the van
Carry a set of NTC sensors, an ignition electrode kit and a fan for Ariston — these three parts clear >70% of 501 call-outs.
Recommission
After the fix, run the Ariston 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 501 without changing parts?
- Only if the fault has cleared (e.g. low pressure repressurised). Persistent 501 means a hardware failure.
- Which is the most common cause of Ariston 501?
- On Ariston boilers, 501 most often points to the sensor or actuator matching its meaning (no flame detected); 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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