Baxi E10 Fault Code: Causes, Fixes & Repair Costs
What does the Baxi E10 fault code mean?
The E10 fault code on a Baxi boiler points to a problem with the outdoor (external) temperature sensor. This sensor feeds real-time outside temperature data to the boiler's PCB so it can fine-tune its output — a feature known as weather compensation. When the boiler detects that the sensor is disconnected, reading outside its expected range, or returning implausible values, it logs E10 and may lock out to protect performance. On most modern Baxi models (Duo-tec, Platinum, and combi ranges) this is the accepted meaning. On a small number of older or variant models, E10 has been associated with a central heating NTC or low water pressure condition — if you are unsure which applies to your boiler, check the model-specific manual or ask a Gas Safe engineer.
General guidance only — not a substitute for professional advice. 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 damaged outdoor NTC thermistor Common
The outdoor sensor contains a small thermistor that changes resistance with temperature. Over time — particularly after exposure to damp, frost, or UV — the thermistor can drift out of range or fail entirely, causing the boiler to log E10. This is the single most common root cause.
- Loose, corroded, or broken sensor wiring Common
The cable running from the external sensor to the boiler PCB is often routed through an external wall and can suffer from chafing, rodent damage, water ingress into connectors, or simply a loose plug at the PCB end. A break or short anywhere in this run will produce the same fault as a dead sensor.
- Outdoor sensor not installed or disabled in software Sometimes
If a previous engineer removed or bypassed the outdoor sensor without disabling weather compensation in the boiler's settings, the boiler will keep looking for a sensor that is no longer present and raise E10. This is particularly common after a boiler service or control upgrade.
- Faulty PCB Rare
If the sensor itself tests within its correct resistance range and the wiring is intact and well-connected, the fault lies with the PCB input circuit that reads the sensor signal. PCB failure is the least likely cause of E10 but cannot be ruled out once the sensor and wiring have been verified.
How to fix it
- Check whether the outdoor sensor is actually fitted DIY safe
Look on an external wall near the boiler — the sensor is usually a small plastic housing about the size of a matchbox. If it has been removed or is visibly damaged (cracked casing, water inside, corroded connector), this is almost certainly your fault. Note what you find before calling an engineer.
- Inspect the sensor cable where it enters the building DIY safe
Follow the sensor cable from the outdoor unit to where it passes through the wall. Look for obvious damage: kinks, cuts, pinch points, or sections where the outer sheath has worn away. Do not attempt to repair the wiring yourself — just note the location of any damage to report to your engineer.
- Check the boiler's outdoor sensor reading in the diagnostic menu DIY safe
Many Baxi models allow you to view live sensor data via the IP or installer parameters menu (refer to your specific model's manual for the correct access sequence). The outdoor sensor reading should broadly match the actual outside temperature. A reading of -40 °C, 130 °C, or a dashes display confirms the boiler cannot see the sensor at all.
- Reset the boiler (up to twice) DIY safe
Once you have noted any visible issues, press and hold the reset button for roughly 3 seconds and allow the boiler to restart. If E10 clears and the boiler runs normally, monitor it for 24 hours. If the code returns, do not keep resetting — persistent faults need a proper diagnosis, not repeated resets.
- Call a Gas Safe registered engineer to test, repair, or replace the sensor and wiring Gas Safe engineer
An engineer will use a multimeter to check the sensor's resistance against the manufacturer's temperature-resistance curve, test continuity along the full cable run, inspect the PCB connector, and replace whichever component has failed. If the sensor and wiring both pass, they will assess whether the PCB requires replacement. All component replacement on a Baxi boiler must be carried out by a Gas Safe registered engineer.
Parts you may need
- Baxi outdoor temperature sensor (NTC thermistor) · from £45
- Sensor cable/extension lead · from £18
- PCB (if sensor and wiring test healthy) · from £220
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 £100–£220, depending on the underlying cause.
Frequently asked questions
Can I use my Baxi boiler with the outdoor sensor disconnected?
Many Baxi boilers will continue to run for heating and hot water without an outdoor sensor — they simply revert to a fixed flow-temperature mode rather than using weather compensation. However, the E10 fault code will remain displayed and the boiler may run less efficiently. If you do not want or need weather compensation, a Gas Safe engineer can disable the outdoor sensor function in the boiler's parameters so the fault no longer appears.
How much does it cost to fix a Baxi E10 fault in the UK?
For the vast majority of E10 faults — a failed sensor or damaged wiring — you should expect to pay somewhere between £100 and £220 including parts and labour. The outdoor sensor itself typically costs £30–£60 for the part, and most engineers can replace it within an hour. If the fault turns out to be a PCB problem, costs rise considerably: PCBs for Baxi boilers typically cost £180–£350 for the part alone, pushing the total repair bill to £280–£450 or more, though PCB failure as the cause of E10 is uncommon.
Is E10 the same fault on all Baxi models?
On most modern Baxi models — including the Duo-tec, Platinum, and combi ranges — E10 consistently means an outdoor or external temperature sensor fault. On a small number of older Baxi models the same code has been linked to a central heating NTC sensor fault or low system pressure. If your boiler is an older model and the outdoor sensor appears fine, check your system pressure (it should sit between 1 and 1.5 bar when cold) and consult the model-specific manual or an engineer.
Why has my Baxi shown E10 only now if the outdoor sensor has been there for years?
Outdoor sensors degrade gradually through repeated exposure to frost, moisture, and temperature cycling. The thermistor's resistance can drift slowly until it finally moves outside the boiler's acceptable range, triggering E10. A spell of very cold or very wet weather often pushes a borderline sensor over the edge, which is why faults like this tend to appear in winter rather than summer. Wiring corrosion at the outdoor connector follows the same seasonal pattern.