The E16 fault code appears on 4 boiler brands — Alpha, Andrews, Johnson & Starley and Warmflow — and on all of them it points to the same kind of problem. The details still differ by brand (thresholds, sub-codes, reset procedure), so use the table below to jump to the page for your boiler.
The brand is printed on the front casing. Tap your brand for the full causes, fixes and repair costs.
| Brand | What E16 means | Severity | DIY? |
|---|---|---|---|
A Alpha | The E16 code on an Alpha boiler signals a fan fault. Full guide → | Lockout — engineer likely | No |
A Andrews | The E16 fault on Andrews boilers most commonly indicates a problem with the return or flow water temperature sensor (NTC thermistor). Full guide → | Lockout — engineer likely | No |
JS Johnson & Starley | E16 on a Johnson & Starley unit is a sensor stuck lockout: a monitored temperature sensor's reading has stopped moving when it should be changing. Full guide → | Lockout — engineer likely | No |
W Warmflow | The E16 code on a Warmflow boiler signals that the control board has detected a problem with the flue fan. Full guide → | Lockout — engineer likely | No |
The E16 code on an Alpha boiler signals a fan fault. The boiler's fan is responsible for safely drawing combustion gases out through the flue — without it running correctly, toxic exhaust fumes could back up into the property. As a safety measure, the boiler immediately shuts down and locks out until the fan issue is resolved. The fault can stem from the fan itself, its wiring, or the PCB that commands it to run.
The E16 fault on Andrews boilers most commonly indicates a problem with the return or flow water temperature sensor (NTC thermistor). The boiler's control board has detected a temperature reading that is outside the expected range, or cannot communicate reliably with the sensor, triggering a safety lockout. On some Andrews models that share architecture with other European platforms, E16 can instead relate to a fan-speed fault — the control board has not received the expected signal from the fan during operation. Because Andrews does not publish a single unified fault-code list covering all its ranges, the precise meaning can differ between models: always cross-reference with the label inside your boiler's casing or the model-specific manual before proceeding.
E16 on a Johnson & Starley unit is a sensor stuck lockout: a monitored temperature sensor's reading has stopped moving when it should be changing. During heat-up and cool-down the controller expects every temperature it watches to track the appliance's behaviour; a value that sits flat through a firing cycle is a failed sensor, not a stable temperature, and the unit locks out rather than control against it. E16, E17 and E18 form a family — the same stuck-sensor supervision applied to different sensor channels — so the on-site job is the same for each: identify which probe has frozen, confirm with a resistance check, and replace it.
Causes, fixes & costs for Johnson & Starley E16 → · All Johnson & Starley codes
The E16 code on a Warmflow boiler signals that the control board has detected a problem with the flue fan. The fan's job is to push combustion gases safely out of your home through the flue — without it working correctly, the boiler's electronics will refuse to fire the burner as a precaution. This is a deliberate safety lockout: the boiler shuts itself down rather than risk harmful gases building up inside. Because gas components are involved, diagnosing and fixing E16 is a job for a Gas Safe registered engineer.
Causes, fixes & costs for Warmflow E16 → · All Warmflow codes
Broadly, yes — on Alpha, Andrews, Johnson & Starley and Warmflow the E16 code points to the same class of fault, and the recommended response is similar. Model-specific details such as sub-codes and reset procedures still vary, so follow the page for your own brand.
Not usually. On every brand listed, E16 points to a fault that needs a suitably registered engineer to diagnose and repair. A single reset to rule out a transient glitch is reasonable; repeated resets are not.
For gas boilers, a Gas Safe registered engineer — it is a legal requirement for any work on the appliance. If you smell gas at any point, leave the property and call the National Gas Emergency line on 0800 111 999.
General guidance only — not a substitute for professional advice, and not certified by a registered engineer. Any work on a gas appliance must be carried out by a Gas Safe registered engineer. If you smell gas, call 0800 111 999.
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