Chaffoteaux 253 Fault Code: Causes, Fixes & Repair Costs
What does the Chaffoteaux 253 fault code mean?
'253' does not appear as a confirmed, standalone fault code in Chaffoteaux's published error code tables. If your Chaffoteaux boiler is displaying something that looks like 253, there are two likely explanations. First, on models fitted with the Expert Control system, fault codes are shown as two-part numbers (for example '2 53' or '1 01'); the digits may run together on the display and be misread as '253'. Second, older Chaffoteaux models — including the Britony, Pigma, Urbia, Talia, Calydra, and MX2 ranges — often use flashing light sequences rather than a numeric display, so what you see may not be a conventional fault code at all. The '2 xx' range on Expert Control boards generally relates to flow and system-filling issues; however, '2 53' specifically is not published in the available tables. The safest course is to locate your exact model number, cross-reference the code against your model's manual, and if the fault persists, call a Gas Safe registered engineer with both pieces of information.
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
- Display misread — two separate codes shown in sequence Common
Chaffoteaux Expert Control boilers display faults as two-part codes. If the display briefly shows '2' then '53', or cycles through multiple codes, a homeowner can easily read this as the single number '253'. Check whether the digits flash separately or together before assuming it is one code.
- Low system pressure Common
Across the Chaffoteaux range, low water pressure (below 1 bar when cold) triggers a lockout and can cause unusual or incomplete code displays. A pressure gauge below 1 bar is a quick thing to check before anything else.
- Ignition or flame-detection failure Common
A faulty ignition electrode, a dirty or damaged flame sensor, or a brief interruption to the gas supply can all cause the boiler to lock out after a failed start attempt. The boiler may display an error — including an unfamiliar code — and refuse to restart until the underlying ignition problem is resolved.
- Frozen or blocked condensate pipe Common
In cold weather the condensate pipe — the white plastic pipe that exits through an outside wall — can freeze solid, preventing the boiler from operating. This is one of the most common winter lockout causes across all Chaffoteaux models.
- Gas supply interruption Sometimes
If the gas supply to the property is interrupted — whether due to a closed meter valve, an empty prepayment meter, or a wider supply issue — the boiler will fail to ignite and lock out. Other gas appliances in the home will also stop working.
- PCB or sensor fault generating an unrecognised code Sometimes
A failing printed circuit board (PCB) or a faulty thermistor/sensor can cause the control system to display codes that do not match the standard published table. This is more common on boilers that are eight or more years old.
- Flue or air-supply obstruction Rare
A blockage or restriction in the flue, or a problem with the fan that draws combustion air, can prevent safe ignition and trigger a lockout with an error code that may be difficult to identify without specialist diagnostic equipment.
How to fix it
- Locate your exact boiler model number DIY safe
Find the model label — usually on the front panel, inside the casing door, or on the underside of the boiler. Write down the full model name and any serial number. This is essential for looking up the correct fault code table and for giving accurate information to an engineer.
- Check your boiler manual for the correct fault code table DIY safe
Download the manual for your specific model from the Chaffoteaux or Ariston website, or from ManualsLib. Look up what '253', '2 53', or the combination of flashing lights actually means for your model. Many Chaffoteaux faults are expressed as two-part codes or light sequences that look different to a simple three-digit number.
- Check your system pressure DIY safe
Look at the pressure gauge on the boiler. It should read between 1.0 and 1.5 bar when the heating is cold. If it has dropped below 1 bar, use the filling loop (usually a braided flexible hose beneath the boiler) to top it up slowly until the gauge reaches 1.2–1.3 bar, then close the filling loop valve. If you are unsure how to do this safely, stop and call an engineer.
- Check that your gas supply is working DIY safe
Try another gas appliance such as a gas hob. If that also fails to light, check that your meter valve is open and, if you have a prepayment meter, that it has sufficient credit. If there is a wider supply problem, contact your gas supplier (call the National Gas Emergency Service on 0800 111 999 if you suspect a gas leak).
- In cold weather, check the condensate pipe for ice DIY safe
Find the white plastic condensate pipe that exits through an outside wall. If it feels solid or you can see ice around the outlet, it has frozen. You can carefully thaw it using warm (not boiling) water poured over the pipe, working from the boiler end outwards. Once it is clear, reset the boiler once and monitor it.
- Reset the boiler once DIY safe
Press the reset button on your Chaffoteaux boiler and hold it for the duration indicated in your manual (usually around three seconds). Allow the boiler to complete its start-up sequence. If the fault returns within a short time, do not keep resetting — repeated resets without fixing the underlying cause can cause further damage and may be unsafe.
- Call a Gas Safe registered engineer Gas Safe engineer
If the fault code reappears after one reset, or if you cannot identify the code in your model's manual, contact a Gas Safe registered engineer. Provide them with the exact model number and the precise display reading (photograph the display if possible). Any work on gas components, the ignition system, the gas valve, sensors, flue, or PCB must only be carried out by a qualified professional.
Parts you may need
- Ignition electrode · from £35
- Flame sensor (ionisation probe) · from £30
- Condensate trap · from £25
- NTC thermistor (flow or return sensor) · from £20
- Boiler PCB · from £220
- Gas valve · from £110
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 £120–£350, depending on the underlying cause.
Frequently asked questions
Why can't I find fault code 253 in the Chaffoteaux manual?
Because 253 does not appear as a confirmed code in Chaffoteaux's published fault tables for any of their gas boiler ranges. The most likely explanation is that your display is showing two separate codes in sequence — for example '2' followed by '53' — which can look like a single number '253' if you catch the display briefly. On older Chaffoteaux models, errors are shown as flashing light combinations rather than numbers, so a three-digit reading on those machines would not be a standard fault code at all. Always check the fault table in your specific model's manual rather than relying on a generic list.
Is it safe to keep resetting a Chaffoteaux boiler that keeps showing this fault?
No. One reset is reasonable to try after clearing an obvious cause such as a frozen condensate pipe or low pressure. If the boiler locks out again shortly after, repeated resets will not fix the problem and may mask a safety issue. Stop resetting and arrange for a Gas Safe registered engineer to diagnose it properly.
How much does it typically cost to repair a Chaffoteaux boiler showing an unknown fault code?
Most repairs — covering components such as sensors, electrodes, pumps, or minor valve work — fall in the range of £120 to £350 including labour. A gas valve replacement tends to sit towards the top of that range at around £180–£220 all-in. If the PCB turns out to be faulty, costs rise significantly to around £400–£650, and a failed heat exchanger can cost a similar or greater amount. On a boiler that is more than ten years old, a PCB or heat exchanger repair can cost nearly as much as a new boiler installation, so it is worth asking the engineer for an honest comparison before committing to a major repair.
Which Chaffoteaux models use the Expert Control display that shows two-part fault codes?
The Expert Control interface is found on more recent Chaffoteaux condensing boilers. It displays faults in the format 'X XX' — for example, 1 01 for an overheat condition, 1 02 for a pressure sensor error, or 3 07 for a PCB fault. If your boiler has a small digital screen showing two groups of digits, it is likely using this system and the code you see should be read as two separate parts. Older models such as the Britony and Pigma series use LED flash sequences instead, and have no numeric display at all.