Chaffoteaux 207 Fault Code: Causes, Fixes & Repair Costs
What does the Chaffoteaux 207 fault code mean?
Fault code 207 on a Chaffoteaux boiler sits within the 200-series block, which the boiler's control system reserves exclusively for issues with the domestic hot water (DHW) circuit. Code 207 specifically tells you that the boiler has detected a problem with the NTC thermistor responsible for monitoring your hot water temperature — either the sensor is sending a signal that falls outside the expected range, has developed an open or short circuit, or has lost reliable communication with the main control board. Without a trustworthy temperature reading from this sensor, the boiler cannot safely manage DHW delivery and will lock out to protect itself. On a small number of specialist models with solar integration (such as the Flexiflame 120 NL), 207 can instead flag solar manifold overheating, but on standard combi and system boilers the DHW sensor fault interpretation applies. The 201–209 range appears consistently across the Chaffoteaux Mira, Urbia, Serelia, Niagara C, Talia, and Inoa ranges, so if your display shows 207 you are in the right place regardless of which of these models you own.
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 DHW NTC thermistor Common
The sensor itself has failed internally, either developing a short circuit (resistance reads near zero ohms) or an open circuit (resistance reads infinite). At around 25°C a healthy Chaffoteaux NTC sensor should show roughly 8–9 kΩ resistance. Any reading well outside this range confirms the sensor is defective and needs replacing with a genuine Ariston/Chaffoteaux part.
- Loose or corroded wiring connection Common
The plug-in connector linking the DHW sensor to the PCB can oxidise over time, especially in damp boiler cupboards, or may have worked loose. Even a slightly imperfect connection causes resistance fluctuations that the board interprets as a sensor fault. A visual inspection and gentle cleaning of the connector pins often resolves this before any parts are ordered.
- Faulty PCB (main control board) Sometimes
If the sensor tests within its correct resistance range and the wiring is sound, the problem may lie with the PCB itself misreading the sensor signal. Signs of a board problem include visible component damage, scorch marks, or deformed tracks. PCB failure is a less frequent cause but is more expensive to remedy.
- Electrical supply irregularity Sometimes
A voltage spike or power surge — perhaps during a power cut and restoration — can latch a sensor-related error code even when the physical sensor is undamaged. A single reset after restoring power is worth trying first. Fitting the boiler on a voltage-stabilised spur can help prevent recurrence.
How to fix it
- Reset the boiler once or twice DIY safe
Press and hold the Reset button on the boiler's front panel as described in your user manual. If the fault clears and does not return, monitor the boiler over the next few hours. Avoid pressing Reset more than two or three times in quick succession — repeated resets in a short period can trigger additional lockout codes and will not address the underlying fault.
- Check your gas supply and mains power DIY safe
Confirm that other gas appliances in your home (hob, fire) are working normally, that the gas isolation valve on the boiler supply pipe is fully open, and that the boiler has a stable mains electricity supply. Rule out a power interruption as the cause before assuming a component fault.
- Have a Gas Safe engineer inspect the DHW sensor wiring Gas Safe engineer
A registered engineer will remove the sensor connector from its socket and examine the pins and wires for corrosion, oxidation, heat damage, or poor contact. Connector pins can be carefully cleaned if necessary. This simple check takes only minutes and can save the cost of an unnecessary part replacement.
- Have the engineer test the NTC thermistor with a multimeter Gas Safe engineer
With the boiler isolated from power, the engineer measures the sensor's resistance across its terminals. At approximately 25°C ambient temperature the reading should fall in the region of 8–9 kΩ for a healthy sensor. A reading of zero indicates a short circuit; an infinite reading indicates an internal break — either way the sensor is beyond use and must be replaced.
- Replace the DHW NTC thermistor if confirmed faulty Gas Safe engineer
Genuine Ariston/Chaffoteaux DHW temperature sensors (for example part 61000733) are widely available from UK boiler spares stockists at roughly £10–£20 including VAT. The engineer should apply a small amount of thermal paste when fitting the new sensor to ensure accurate temperature transfer from the pipework surface to the sensor tip.
- Assess the PCB if the sensor and wiring are both sound Gas Safe engineer
If the replacement sensor does not clear the fault, the engineer will carry out further diagnostic checks on the main control board. PCB replacement is a more involved and costly repair; on an older boiler the engineer may advise weighing up the cost against investing in a new appliance.
- Call a Gas Safe registered engineer if you have not already done so Gas Safe engineer
All internal boiler work is legally required to be carried out by a Gas Safe registered engineer in the UK. You can verify any engineer's credentials on the official Gas Safe Register at gassaferegister.co.uk. Do not attempt to access internal components yourself.
Parts you may need
- Chaffoteaux DHW NTC thermistor (e.g. Ariston part 61000733) · from £15
- Sensor wiring loom / connector harness · from £25
- Chaffoteaux main PCB (model-specific) · from £180
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–£280, depending on the underlying cause.
Frequently asked questions
Can I fix Chaffoteaux fault code 207 myself without an engineer?
The only homeowner-safe steps are resetting the boiler (once or twice) and checking that your gas supply and mains power are both on. Everything beyond that — opening the boiler casing, testing the sensor, or replacing any component — must be done by a Gas Safe registered engineer. This is a legal requirement in the UK, not just a recommendation.
How much does it cost to fix a Chaffoteaux 207 fault code in the UK?
If the fault is simply a failed DHW NTC thermistor, most people pay in the region of £100–£180 all-in, as the part itself is inexpensive (around £10–£20) and the labour time is modest. If the PCB turns out to be at fault, costs typically rise to £200–£400 or more depending on the model and parts availability. On an older boiler it is worth asking your engineer whether a PCB repair makes financial sense compared with replacing the appliance.
Which Chaffoteaux boiler models show fault code 207?
The 200-series fault codes — including 207 — are used across the main range of modern Chaffoteaux combi and system boilers, including the Mira, Urbia, Serelia, Niagara C, Talia, Inoa, and Pigma. On the specialist Flexiflame 120 NL with solar integration, 207 instead relates to solar manifold overheating rather than the DHW sensor, so always cross-reference with your model's handbook if you are unsure.
My Chaffoteaux keeps showing 207 after I reset it — what does that mean?
A fault code that clears on reset but returns repeatedly almost always points to a genuine component problem rather than a one-off glitch. In the case of 207 the most likely culprits are a degraded DHW NTC sensor or a corroded wiring connection. Repeated resets will not resolve a hardware fault and can in some cases trigger additional lockout codes. Book a Gas Safe engineer to carry out a proper diagnosis before the situation escalates.