Andrews E16 Fault Code: Causes, Fixes & Repair Costs
What does the Andrews E16 fault code mean?
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.
General guidance only — not a substitute for professional advice, and not certified by a Gas Safe engineer. Always have your specific appliance assessed by a qualified professional. Any gas work must be carried out by a Gas Safe registered engineer. If you smell gas or suspect carbon monoxide, leave the property and call the National Gas Emergency line on 0800 111 999.
Common causes
- Faulty or degraded NTC temperature sensor Common
The NTC thermistor that monitors return or flow water temperature has drifted out of specification, developed an open or short circuit, or simply failed with age. This is the most common reason E16 appears on boiler platforms used in Andrews units. The boiler locks out as a safety precaution when sensor readings become unreliable.
- Loose or corroded wiring to the sensor Common
The plug connector between the NTC sensor and the PCB can work loose due to vibration, or the terminals can corrode over time — particularly in plant rooms with damp or dusty conditions. A poor connection mimics sensor failure and generates the same lockout code.
- Fan fault or loss of fan speed signal Sometimes
On Andrews models that share an Alpha-derived platform, E16 can flag a fan-related problem rather than a sensor issue. If the fan fails to reach its target speed — due to a worn motor, a blocked flue, or a seized bearing — the control board registers a safety fault and locks out the boiler.
- PCB failure or communication error Rare
If the control board itself is malfunctioning, it may misread valid sensor or fan signals and generate a spurious E16. PCB faults are less common than sensor or wiring issues but should be considered if component tests come back normal.
How to fix it
- Note the full code displayed and check your model manual DIY safe
Before doing anything else, look for a label inside the boiler's casing or in your user manual to confirm what E16 means on your specific Andrews model. If the display shows any supplementary digits alongside E16, record them — these sub-codes can point an engineer directly to the affected component.
- Attempt a single boiler reset DIY safe
Press and hold the reset button as described in your user guide (usually 3–5 seconds). Allow the boiler a full ignition cycle before deciding whether the fault has cleared. Do not reset more than once or twice — repeatedly forcing the boiler to run through lockout can mask the underlying problem and make professional diagnosis harder.
- Check that your gas supply is on DIY safe
Confirm other gas appliances in the property (hob, fire) are working normally. If there is a wider gas supply interruption, contact your gas supplier rather than continuing to reset the boiler.
- Inspect wiring and sensor connections — engineer only Gas Safe engineer
A Gas Safe engineer will remove the boiler casing and visually inspect the wiring harness leading to the NTC sensor(s) and fan. They will reseat any loose connectors, check for signs of heat damage or corrosion, and test cable continuity with a multimeter.
- Test the NTC thermistor resistance — engineer only Gas Safe engineer
The engineer will measure the sensor's resistance at a known water temperature and compare it against the manufacturer's resistance table. A reading that falls well outside the expected curve confirms sensor failure and points to a straightforward replacement.
- Assess fan operation and speed signal — engineer only Gas Safe engineer
If E16 is flagging a fan fault on your model, the engineer will check the fan's electrical supply, measure its actual speed output, and inspect the flue for partial blockages that could be loading the motor. A seized or underpowered fan will need replacing.
- Evaluate and replace the PCB if required — engineer only Gas Safe engineer
If both the sensor and fan test satisfactorily, the control board is the most likely remaining culprit. PCB diagnosis and replacement must be carried out by a qualified engineer, as incorrect handling can cause further damage or create a safety hazard.
- Call a Gas Safe registered engineer DIY safe
If the fault returns after a single reset, or if you have not been able to identify a simple cause such as a gas supply interruption, contact a Gas Safe registered engineer. All internal inspection, component testing, and parts replacement on an Andrews boiler must be carried out by a qualified professional.
Parts you may need
- NTC return/flow temperature sensor (thermistor) · from £25
- Sensor wiring harness · from £35
- Boiler fan/flue fan assembly · from £120
- PCB (main control board) · from £280
The exact spare depends on your boiler's GC number (on the data badge). Check this against the part before buying.
Typical repair cost
Expect to pay roughly £130–£380, depending on the underlying cause.
Frequently asked questions
Can I fix Andrews E16 myself by resetting the boiler?
A single reset is worth trying — occasionally a transient voltage spike or brief sensor glitch will trigger E16 and a reset clears it permanently. However, if the code returns after one or two resets, the boiler is telling you there is a genuine fault. Repeatedly resetting to keep the boiler running is not safe practice and can make the engineer's diagnosis harder. All internal work — sensor replacement, wiring checks, fan or PCB repairs — must be done by a Gas Safe registered engineer.
How much does it cost to fix E16 on an Andrews boiler?
For the most common cause — an NTC temperature sensor replacement including an engineer's call-out and labour — most homeowners pay in the region of £130 to £250. If the fan needs replacing the bill typically rises to £250–£380. In the rarer situation where the PCB is at fault, parts alone can cost £180–£350 on top of labour, so total costs can exceed £500; however, this scenario is much less common and a good engineer will exhaust cheaper possibilities first.
What is the difference between E16 and other temperature-sensor codes on Andrews boilers?
Andrews uses a range of error codes for different sensor positions and fault types. E16 is most frequently associated with the return or flow NTC thermistor entering lockout, whereas codes such as E01 and E02 typically relate to ignition or flame-detection failures. On models with Alpha-platform architecture, E16 can indicate a fan fault rather than a sensor fault, which is why confirming the code meaning against your specific model's documentation matters before any repair work begins.
Will an annual service help prevent E16 from appearing?
Yes. During a service, an engineer cleans sensor probes, checks wiring connections, tests the fan, and verifies that all electrical contacts are secure and corrosion-free. Catching a marginal sensor or a slightly loose connector at service time costs far less than an emergency call-out when the boiler locks out in cold weather. Andrews recommend annual servicing to maintain both efficiency and warranty validity.