Chaffoteaux 114 Fault Code: Causes, Fixes & Repair Costs
What does the Chaffoteaux 114 fault code mean?
Fault code 114 on Chaffoteaux boilers most commonly indicates a problem with the outdoor (external) temperature sensor — either a short circuit, open circuit, or the sensor being completely disconnected. On modern models such as the Talia and Inoa, the boiler uses this sensor (or an internet-sourced external temperature feed) to optimise heating output, so when the reading is unavailable the boiler flags a fault. Some models may still provide heat while the fault is active, but efficiency and weather compensation are compromised. On older models such as the Mira Green Ultra 30, code 114 can instead point to a control board or internal communication fault, often triggered by a power outage or supply interruption. Knowing your exact model is important — if you recently had a smart thermostat fitted or experienced a power cut, that context will help an engineer diagnose the fault quickly.
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
- Loose or disconnected outdoor sensor wiring Common
The most frequent trigger on modern Chaffoteaux models. The external sensor connects to the boiler via a low-voltage wiring circuit, and the connections at the terminal block can work loose over time or be disturbed during other work — particularly when a smart thermostat (such as a Tado or Hive) has recently been installed.
- Failed or corroded outdoor temperature sensor Common
The sensor itself is a small weatherproof housing containing a thermistor. Prolonged outdoor exposure, moisture ingress, or age can cause the thermistor to drift out of range or fail entirely. An engineer can confirm this quickly by checking the sensor's resistance with a multimeter against the manufacturer's temperature-resistance table.
- Boiler not configured to match sensor presence Sometimes
If the boiler's internal parameters are set to expect an external sensor but none is physically fitted — or vice versa — it will raise fault 114. This can happen after a service or control board replacement where settings were not restored correctly.
- Power outage causing communication or reset error Sometimes
On older Chaffoteaux models (particularly the Mira Green Ultra and Bonjour ranges), a sudden loss of mains power can cause a communication error between internal boards that manifests as fault 114 on restart. A clean power cycle sometimes clears this, but if it recurs the control board may need attention.
- Faulty or failing PCB (control board) Rare
On the Mira Green Ultra 30 in particular, fault 114 is documented as a control board fault. If all sensor wiring and connections check out correctly, the PCB itself may be the root cause. PCB failure is less common but significantly more costly to resolve.
How to fix it
- Switch the boiler off and remove it from mains power for at least 5 minutes, then power it back on and attempt a reset using the boiler's reset button. DIY safe
A brief loss of mains power — from a power cut or a tripped circuit — can cause a spurious fault 114 on some Chaffoteaux models, particularly older ones. A full power cycle (not just pressing reset) gives the system a clean restart. Only attempt this once or twice; if the fault code returns promptly, move on rather than repeatedly resetting.
- Check that the outdoor temperature sensor is physically in place and that its cable is not visibly damaged, pinched, or disconnected at the boiler end. DIY safe
The external sensor is usually mounted on a north-facing exterior wall and connected to the boiler by a two-core cable. You can visually inspect the cable run for obvious damage and check that it is firmly plugged into the correct terminals at the boiler's terminal block — without removing any boiler casing. Do not attempt to open the boiler or work inside it.
- If a smart thermostat was recently installed, check whether the installer disturbed the sensor wiring or altered the boiler's parameter settings. DIY safe
Third-party smart thermostat installations occasionally result in low-voltage sensor cables being disconnected or terminal screws being loosened. If you can see the terminal block without removing the boiler casing, check that the sensor wires are firmly seated. If in doubt, contact the installer first as this may be covered under their workmanship.
- Have a Gas Safe registered engineer test the outdoor sensor's resistance and inspect internal wiring. Gas Safe engineer
Using a multimeter, an engineer can compare the sensor's resistance reading against the Chaffoteaux resistance-temperature chart for that specific model. A reading outside the expected range confirms a faulty sensor. They will also check internal wiring and connections at the PCB — work that must not be carried out by an unqualified person.
- Have the engineer replace the outdoor temperature sensor if it is confirmed faulty. Gas Safe engineer
Replacement Chaffoteaux outdoor sensors are available through the Ariston Group parts network. The engineer will fit the new sensor, restore all wiring connections, and verify that the boiler's parameters are correctly configured to recognise it. Parts typically cost £25–£100 depending on the model; total cost including labour is usually £80–£200.
- If the sensor and wiring are confirmed sound, have the engineer assess the PCB for a control board fault. Gas Safe engineer
This is more likely on older Mira Green Ultra 30 units or where fault 114 persists after sensor replacement. The engineer will check for secondary fault codes, inspect the PCB for visible damage, and test communications between boards. PCB replacement is a more significant repair — on an older boiler, it may be worth comparing the cost against a new installation.
- If the fault cannot be resolved or the boiler is older and the repair cost is disproportionate, contact a Gas Safe registered engineer to discuss your options. Gas Safe engineer
Chaffoteaux is part of the Ariston Group, so parts support is generally good, but on ageing units a costly PCB repair may not represent good value. A registered engineer can give an honest appraisal of whether repair or replacement is the more sensible route.
Parts you may need
- Chaffoteaux outdoor temperature sensor · from £55
- Sensor cable and connector assembly · from £20
- Chaffoteaux PCB (control board) — model dependent · 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 £90–£280, depending on the underlying cause.
Frequently asked questions
Will my Chaffoteaux boiler still heat my home with fault code 114 showing?
It depends on your model. On many modern Chaffoteaux boilers — particularly the Talia and Inoa — the external sensor is used for weather compensation rather than core operation, so the boiler may continue to fire and provide heating and hot water despite the fault. However, it will not be optimising output based on outdoor temperature, which can increase gas consumption. On some models the boiler will lock out completely. Either way, the fault should be investigated promptly rather than left indefinitely.
Could a recent smart thermostat installation have caused fault code 114?
Yes, this is a known trigger. When a smart thermostat such as a Tado, Hive, or Nest is retrofitted, the installer works at the boiler's terminal block and occasionally disturbs the low-voltage wiring for the outdoor sensor. If fault 114 appeared shortly after a thermostat was fitted, contact the installer first — it may simply be a loose connection that they can reconnect quickly, potentially at no extra charge.
My boiler showed fault 114 after a power cut — do I need an engineer?
Not necessarily straight away. On older Chaffoteaux models (Mira Green Ultra, Bonjour), a power interruption can cause a communication reset that triggers fault 114. Switch the boiler off at the mains for five minutes, then power it back on and reset it. If the fault clears and does not return, the power cut was likely the cause. If it reappears within a short time, there is an underlying issue with the sensor or control board that will need a Gas Safe engineer to diagnose.
How much does a PCB replacement cost on a Chaffoteaux boiler, and is it worth it?
A PCB replacement on a Chaffoteaux boiler typically costs £350–£600 or more once parts and labour are included — the board itself can range from around £180 to £400 depending on the model. On a boiler that is less than eight to ten years old and otherwise in good condition, repair is usually worthwhile. On an older unit, particularly one out of warranty, it is worth getting a written quote and comparing it against the cost of a new boiler. A Gas Safe registered engineer should be able to advise you honestly on this.