How to Fix Potterton E128 Fault Code (Flame Loss During Run) UK
Potterton E128 means flame loss during run. UK diagnosis, parts to order, reset sequence.
What E128 means
Potterton E128 indicates flame loss during run. The boiler will lock out and refuse to fire until the fault is cleared.
Do not simply reset — E128 is stored in the Potterton error log and will re-trigger within minutes if the underlying part has failed.
Diagnostic sequence
Enter service mode on the Potterton boiler and read the flow/return/DHW temperatures, fan PWM, ionisation current and pump speed.
Cross-reference against the Potterton technical manual — E128 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 Potterton test procedure.
Parts to have on the van
Carry a set of NTC sensors, an ignition electrode kit and a fan for Potterton — these three parts clear >70% of E128 call-outs.
Recommission
After the fix, run the Potterton 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 E128 without changing parts?
- Only if the fault has cleared (e.g. low pressure repressurised). Persistent E128 means a hardware failure.
- Which is the most common cause of Potterton E128?
- On Potterton boilers, E128 most often points to the sensor or actuator matching its meaning (flame loss during run); 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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