Chaffoteaux 122 Fault Code: Causes, Fixes & Repair Costs
What does the Chaffoteaux 122 fault code mean?
Fault code 122 on Chaffoteaux boilers is most commonly associated with a fan or air pressure switch failure, or a flow/circulation check fault, depending on your specific model. Chaffoteaux boilers use a structured error numbering system where the first digit indicates which functional unit is involved — codes in the '1' series typically relate to hydraulics, circulation, or airflow. On alphanumeric display models (such as the Expert Control, Talia, Pigma, and Urbia ranges), code 122 is likely a flow-check or circulation-related fault. On older LED-based models (such as the Britony Combi SE), a code in this range can indicate the fan has started but the air pressure switch has not responded correctly, or vice versa. Because Chaffoteaux is part of the Ariston Thermo Group, the underlying fault logic is shared across several related boiler families. Always check your specific model's manual and provide the exact model number to an engineer for a definitive diagnosis.
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
- Fan or air pressure switch fault Common
The boiler fan starts but fails to trigger the air pressure switch, which must signal the PCB before ignition can begin. This can be caused by a blocked flue restricting airflow, a faulty or seized fan motor (worn bearings or burnt-out windings), or a defective air pressure switch that is stuck open or closed. Without this confirmation signal, the PCB locks out the boiler as a safety measure.
- Low system pressure or circulation failure Common
If system pressure has dropped below the boiler's minimum operating threshold (typically around 0.8–1.0 bar), the boiler will stop to protect itself. This is especially common after radiators have been bled, if there is a slow leak anywhere in the system, or if the expansion vessel has lost its pre-charge. On models where code 122 relates to a flow check, a faulty pump or airlocked system can also trigger this fault.
- Blocked or partially obstructed flue Sometimes
A blockage in the flue — caused by bird nests, debris, or damage — prevents combustion gases from being expelled properly. The resulting back pressure can stop the air pressure switch from operating correctly, which triggers the fault. A turbine (fan) that is clogged with debris can produce the same effect without there being an external flue obstruction.
- Faulty thermistor or temperature sensor Sometimes
A damaged or disconnected NTC thermistor (flow or return temperature sensor) can generate a fault in the 1-series code range on alphanumeric Chaffoteaux models. If the sensor circuit reads an open circuit or an implausible temperature value, the boiler will not fire. This is more likely on older boilers or after recent work has been carried out near the sensor wiring.
- PCB fault Rare
If none of the above components are found to be at fault, the PCB itself may be failing to correctly interpret the signals it receives from the fan, air pressure switch, or sensors. PCB faults are relatively uncommon but become more likely on boilers that are over ten years old or have suffered from repeated electrical surges or water ingress.
How to fix it
- Reset the boiler once DIY safe
Locate the reset button on your Chaffoteaux boiler (usually marked with a flame or 'R' symbol) and press it once. Allow the boiler a full minute to attempt a restart. If the fault code returns immediately, do not keep resetting — repeated resets without resolving the root cause can cause further damage and will not fix an underlying component failure.
- Check your system pressure gauge DIY safe
Look at the pressure gauge on the front of the boiler. A healthy cold-system reading is between 1.0 and 1.5 bar. If the needle is below 1.0 bar, the system may need repressurising via the filling loop (two small valves under or near the boiler). Slowly open both valves until the gauge reads approximately 1.2 bar, then close them again. If pressure drops again within a few days, there is likely a leak that needs professional attention.
- Check that your gas supply is working DIY safe
Try another gas appliance in your home — a gas hob or a gas fire. If none of them work, the issue may be with your gas supply rather than the boiler. Check your prepayment meter if applicable, or call your gas supplier. If all other appliances are working normally, the gas supply to the boiler is likely fine.
- In cold weather, check for a frozen condensate pipe DIY safe
Locate the white plastic condensate pipe that exits through an outside wall. In freezing conditions this can ice up and cause a lockout. If it feels solid or icy, you can carefully pour warm (not boiling) water over the external section to thaw it, then reset the boiler. Insulating the pipe afterwards will help prevent a recurrence.
- Have a Gas Safe engineer inspect the fan and air pressure switch Gas Safe engineer
If the above checks do not resolve the fault, the most likely cause is a faulty fan motor, damaged fan impeller, or a defective air pressure switch. A registered engineer will test the fan's electrical supply and rotation, measure the pressure differential across the switch, and replace whichever component has failed. Do not attempt to access or test these parts yourself.
- Have a Gas Safe engineer check the flue for blockages Gas Safe engineer
A qualified engineer can safely inspect the flue terminal and internal flue passages for obstructions such as bird nests, debris, or physical damage. Flue work must not be carried out by an unregistered person, as incorrect flue conditions can lead to dangerous carbon monoxide build-up.
- Have a Gas Safe engineer test the thermistors and wiring Gas Safe engineer
Using a multimeter, an engineer can check whether the NTC flow and return sensors are reading within their expected resistance range and that all wiring connections are secure and undamaged. A faulty sensor is relatively inexpensive to replace and can mimic more serious faults.
- Have a Gas Safe engineer assess the PCB if all other components test satisfactory Gas Safe engineer
If the fan, air pressure switch, sensors, and flue are all confirmed as functioning correctly, the PCB may be the source of the fault. PCB diagnosis and replacement must only be carried out by a qualified engineer, as live electrical components within the boiler present a serious risk.
Parts you may need
- Boiler fan / flue fan assembly · from £85
- Air pressure switch · from £35
- NTC thermistor (flow or return sensor) · from £18
- Circulating pump · from £75
- Expansion vessel · from £45
- PCB (printed circuit board) · 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 £150–£400, depending on the underlying cause.
Frequently asked questions
Is fault code 122 the same on all Chaffoteaux boilers?
No — Chaffoteaux boilers across different ranges use different display systems, so code 122 does not mean exactly the same thing on every model. On newer alphanumeric display models (Expert Control, Talia, Pigma, Urbia), it falls within the '1-series' codes that relate to hydraulics, flow, and airflow. On older LED-based models like the Britony Combi SE, a code in this range typically indicates a fan or air pressure switch issue. Always cross-reference with your specific model's manual and give your Gas Safe engineer the exact model number so they can interpret the code correctly.
Can I fix fault code 122 myself?
There are a few safe checks a homeowner can carry out: topping up system pressure if it has dropped below 1.0 bar, checking the gas supply is on, thawing a frozen condensate pipe in cold weather, and pressing the reset button once. However, if these do not clear the fault, the likely causes — a faulty fan, air pressure switch, thermistor, or PCB — all require a Gas Safe registered engineer to diagnose and repair safely. Attempting gas or electrical component work without registration is illegal and potentially dangerous.
How much does it cost to repair a Chaffoteaux fault code 122?
Most people with this fault pay somewhere between £150 and £400 including parts and labour. A fan replacement typically costs £200–£350 all-in, while an air pressure switch or thermistor replacement is usually at the lower end, around £120–£200. If the PCB needs replacing, costs can rise to £350–£500. For older boilers approaching or beyond 12–15 years, it is worth getting a quote for a new boiler alongside any repair quote, as major component replacements on an ageing boiler may not represent good value.
Could my Chaffoteaux boiler need replacing rather than repairing?
Chaffoteaux boilers typically have a reliable lifespan of around 10–15 years when serviced annually. If your boiler is within that age range and the fault is a relatively simple component like a fan or sensor, repair is usually the right call. However, if it is older, has had multiple faults recently, or the repair involves a heat exchanger (£400–£650+) or PCB alongside other worn components, a Gas Safe engineer may advise that a replacement boiler is the more cost-effective long-term option. Always get a written repair quote before making a decision.