Chaffoteaux 201 Fault Code: Causes, Fixes & Repair Costs
What does the Chaffoteaux 201 fault code mean?
Fault code 201 on Chaffoteaux boilers indicates that the control board has detected a problem with the domestic hot water (DHW) NTC thermistor — the sensor responsible for monitoring the temperature of your hot water supply. The boiler cannot obtain a valid reading from this sensor, either because the circuit is open (broken) or has developed a short circuit, so the boiler shuts down as a precautionary measure. Code 201 sits at the start of the 201–209 range, which covers DHW circuit anomalies across Chaffoteaux Mira, Urbia, Serelia, and Niagara C models. While 201 specifically flags the sensor signal fault itself, codes in this range all relate to the domestic hot water circuit — if your display shows a code between 201 and 209, check your model's manual alongside this guide to confirm the exact sub-fault.
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 an open circuit or a short. This is the single most likely explanation when code 201 appears without any recent maintenance work. NTC thermistors can degrade over time due to heat cycling and moisture exposure, eventually giving the control board an out-of-range resistance value.
- Loose, corroded, or damaged wiring Common
The low-voltage wiring between the DHW sensor and the PCB is vulnerable to corrosion at connector pins, chafing against pipework, or vibration-related loosening. Even a slightly oxidised connector pin can introduce enough resistance to mimic a broken circuit and trigger the fault.
- Sensor incorrectly seated after maintenance Sometimes
If the boiler has recently been serviced, the DHW sensor may not have been refitted properly into its pocket on the hot water outlet pipe. When the sensor sits in free air rather than against the pipe or in its housing, it reads ambient temperature instead of water temperature, producing a wildly incorrect signal that the board rejects.
- Faulty PCB (control board) Sometimes
If the sensor and all its wiring check out correctly, a fault on the PCB itself may be preventing it from processing the sensor signal properly. Look for visible signs such as discolouration, swollen components, or burnt tracks on the board. PCB failure is less common but becomes more likely in older boilers or where there has been a power surge.
- Software configuration mismatch Rare
On certain Chaffoteaux models that do not have an integrated DHW sensor as standard, the control board can generate code 201 if it has been incorrectly configured in software to expect a sensor that is not physically present. This is a rare cause but worth noting for engineers working on atypical installations.
How to fix it
- Reset the boiler once or twice DIY safe
Press the reset button on the boiler's front panel and wait for it to attempt a restart. A single transient glitch — such as a brief power fluctuation — can cause code 201 to appear without an underlying component failure. Limit resets to two or three attempts; repeated resets on a persistent fault will not clear it and may mask the problem.
- Check your gas and hot water supply DIY safe
Make sure your gas supply is turned on at the meter and that other gas appliances in the home are working normally. Also confirm that the cold water supply to the boiler is not isolated. These basic checks take only a moment and rule out supply-side issues before you call an engineer.
- Inspect wiring connections at the DHW sensor (engineer) Gas Safe engineer
A Gas Safe engineer will access the DHW sensor connector, checking for pin corrosion, moisture ingress, or loose terminals. Oxidised contacts are cleaned and the connector is refitted securely. The wiring loom back to the PCB is also inspected for chafing or breaks.
- Verify the sensor is correctly positioned in its housing (engineer) Gas Safe engineer
The engineer will confirm the NTC thermistor is seated properly in its pocket on the hot water outlet pipe, typically beneath an insulating sleeve. If it has been dislodged, repositioning it correctly can resolve the fault without any parts being needed.
- Test sensor resistance and replace if faulty (engineer) Gas Safe engineer
Using a multimeter, the engineer measures the sensor's resistance across its expected temperature range and compares the reading against the manufacturer's specification. If the reading is out of range or unstable, the NTC thermistor is replaced. The part is inexpensive and the job is straightforward for a qualified engineer.
- Inspect and replace the PCB if sensor tests satisfactory (engineer) Gas Safe engineer
Should the sensor, connectors, and wiring all prove to be in good order yet the fault persists, the PCB is the likely culprit. The engineer will examine the board for visible damage. PCB replacement is significantly more expensive than a sensor swap, so confirming the sensor is truly healthy first is important before committing to this repair.
- Call a Gas Safe registered engineer Gas Safe engineer
If the reset has not cleared code 201, book a Gas Safe registered engineer to carry out the diagnostic steps above. All internal boiler work — including handling sensors, wiring, and the PCB — must be performed by a qualified professional. You can verify an engineer's Gas Safe registration at gassaferegister.co.uk.
Parts you may need
- Chaffoteaux DHW NTC thermistor (e.g. part 61000733) · from £21
- Chaffoteaux DHW sensor wiring harness / connector · from £18
- Chaffoteaux replacement PCB · 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–£250, depending on the underlying cause.
Frequently asked questions
Can I fix Chaffoteaux fault code 201 myself?
The only safe DIY actions are resetting the boiler (no more than two or three times) and checking that your gas supply is turned on. The actual diagnosis and repair — testing the sensor, inspecting wiring, and replacing any components — must be carried out by a Gas Safe registered engineer. Working inside the boiler without the correct qualifications is illegal for gas work and potentially dangerous.
How much does it cost to fix fault code 201 on a Chaffoteaux boiler?
If the fault is caused by the DHW NTC thermistor, which is the most common cause, total repair costs including call-out, labour, and parts typically fall between £100 and £200. The sensor part itself is inexpensive at around £7–£21. If the PCB turns out to be at fault, costs rise considerably — PCB replacement on a Chaffoteaux boiler generally runs between £450 and £700 once parts and labour are included, so it is worth asking your engineer to confirm the sensor is genuinely healthy before agreeing to a board replacement.
Why has my Chaffoteaux boiler shown code 201 after a recent service?
Code 201 appearing shortly after a service is a strong indicator that the DHW sensor was not refitted into its housing correctly. The sensor sits in a pocket on the hot water outlet pipe, often covered by an insulating sleeve, and if it is left slightly displaced it will read air temperature rather than water temperature, which the control board rejects as an invalid signal. Contact the engineer who carried out the service — repositioning the sensor is a quick fix and should be covered under their workmanship.
Is it worth repairing a Chaffoteaux boiler showing code 201, or should I replace it?
For a fault code 201 caused by a faulty DHW sensor, repair almost always makes financial sense — the cost is low and the fix is reliable. If the investigation reveals a failed PCB and the boiler is already over 10–12 years old, it is worth weighing repair cost against replacement, since a new boiler may be a better long-term investment. An annual service is also a practical step to catch early signs of sensor and component wear before they cause a breakdown.