Chaffoteaux 430 Fault Code: Causes, Fixes & Repair Costs
What does the Chaffoteaux 430 fault code mean?
Fault code 430 on a Chaffoteaux boiler sits within the 4xx functional group, which covers zone control, temperature sensing, and regulation faults. On newer models such as the Talia Green, Inoa, and Expert Control series, code 430 points to a problem with the ambient or room temperature sensor circuit — the boiler is receiving a signal that is missing, out of range, or implausible. This can mean the sensor itself has failed, its wiring has an open circuit or short circuit, or there is corrosion on the connector. On certain older Chaffoteaux models where a display is not fitted and codes are shown via indicator light combinations, 430 can instead relate to a system water pressure fault — either too high or too low. Always cross-reference with your specific model's manual, as the Chaffoteaux range (Britony, Talia, Pigma, Inoa, MX2, Calydra and others) uses codes differently across generations.
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 or disconnected room/ambient temperature sensor Common
The most frequent trigger for a 430 on newer Chaffoteaux models. If the sensor develops an open circuit — due to age, a broken wire, or a loose plug — the boiler cannot read a valid ambient temperature and raises a 4xx regulation fault. The boiler will typically lock out until the sensor is replaced or reconnected.
- Moisture or corrosion on sensor connectors Common
Damp conditions inside the boiler casing or behind a wall-mounted room sensor can cause corrosion on the low-voltage connectors. This creates a high-resistance or intermittent contact that the control board interprets as a sensor fault. The code may clear temporarily after a reset but will return.
- Low system water pressure Sometimes
On some Chaffoteaux models, the 430 code signals that water pressure has dropped below the minimum operating threshold (typically around 0.5–0.8 bar). This commonly follows bleeding radiators, a slow system leak, or the expansion vessel losing its air charge. The boiler shuts down to protect the heat exchanger.
- Short circuit in the temperature sensor circuit Sometimes
A short circuit across the sensor terminals gives the control board an implausibly high temperature reading. This can happen if insulation on sensor wiring has worn through and the wires touch each other or the boiler casing.
- PCB (control board) failure Rare
If the PCB's sensor-input circuitry is damaged — by a power surge, moisture ingress, or component ageing — it may misread or fail to read the sensor entirely, producing a 430 fault even when the sensor itself is in good condition. PCB failure is the least common cause but should be considered after the sensor and wiring have been ruled out.
How to fix it
- Check the system pressure gauge DIY safe
Look at the pressure gauge on the boiler's fascia. It should read between 1.0 and 1.5 bar when the system is cold. If it reads below 1.0 bar, the system needs repressurising via the filling loop (two braided-hose valves, usually beneath the boiler). Open both valves slowly, allow pressure to rise to around 1.2–1.3 bar, then close both valves. If you are unsure where the filling loop is or have never used it before, stop and call an engineer.
- Reset the boiler once DIY safe
Locate the reset button on your Chaffoteaux boiler (usually a dedicated button or a held-down mode button — check your model's quick-start guide). Press it once and allow the boiler a full minute to attempt a restart. If the fault code returns immediately or within a short time, do not keep resetting; repeated resets without identifying the root cause can mask developing problems or cause further damage.
- Inspect the room thermostat or sensor wiring for obvious damage DIY safe
Look at the room thermostat or any external temperature sensor connected to the boiler. Check for loose terminal connections, visibly damaged cable, or signs of moisture. Do not open the boiler casing. If you spot a clearly disconnected plug at the thermostat end, you can push it firmly back in. Any work inside the boiler casing must be left to an engineer.
- Check for a frozen condensate pipe (in cold weather) DIY safe
If the fault has appeared during a cold snap, go outside and look for a white plastic pipe (typically 21–32 mm diameter) exiting through an external wall near the boiler. If it appears blocked with ice, you can gently thaw it using warm (not boiling) water poured along its length, or a wrapped hot-water bottle. Once thawed, reset the boiler once. This step is only relevant if your boiler is also showing a condensate-related lockout alongside the 430 code.
- Have a Gas Safe engineer test and replace the temperature sensor Gas Safe engineer
A registered engineer will use a multimeter to measure the resistance of the ambient or room temperature sensor across its operating range and compare it to the manufacturer's specification. If the reading is open-circuit, short-circuit, or drifted out of range, the sensor and its wiring harness will be replaced. On Chaffoteaux Talia and Inoa models this is typically a straightforward job.
- Have the engineer inspect the expansion vessel and system pressure components Gas Safe engineer
If low or high pressure is suspected as the cause on your particular model, an engineer will check the expansion vessel's pre-charge pressure (using a Schrader valve and gauge), recharge or replace the vessel as needed, and inspect the pressure relief valve for weeping or blockage. A pressure relief valve that has been lifting repeatedly may need replacement to prevent recurrence.
- Have the engineer test and replace the PCB if all other causes are ruled out Gas Safe engineer
If the sensor and all wiring check out correctly but the fault persists, the control board's sensor-input circuitry is likely damaged. The engineer will confirm this by substitution or bench testing before ordering a replacement PCB for your specific Chaffoteaux model. Given the cost of a PCB, always ask the engineer to rule out cheaper causes first.
- Call a Gas Safe registered engineer if the fault returns after your safe checks Gas Safe engineer
If system pressure is correct, you have reset the boiler once, and the 430 code keeps reappearing, the fault requires professional diagnosis. When calling, have your boiler model name, serial number (usually on a label inside the casing), and the exact code ready so the engineer can arrive with the most likely replacement parts.
Parts you may need
- Room/ambient temperature sensor · from £35
- Sensor wiring harness · from £25
- Expansion vessel (replacement) · from £55
- Pressure relief valve · from £30
- PCB/control board · 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 £120–£350, depending on the underlying cause.
Frequently asked questions
Is Chaffoteaux fault code 430 always the same fault on every model?
No. Chaffoteaux covers a wide range of boilers — Britony, Talia, Pigma, Inoa, MX2, Calydra and more — and the meaning of code 430 differs between older and newer generations. On current models such as the Talia Green and Inoa it typically indicates a room or ambient temperature sensor fault within the 4xx regulation group. On some older models without a display, the same numeric code can point to a water pressure issue. Always check your specific model's manual, or tell the engineer exactly which model and serial number you have.
Can I fix a Chaffoteaux 430 fault myself?
A few safe checks are within a homeowner's scope: verifying the system pressure is between 1.0 and 1.5 bar and topping it up via the filling loop if low, checking for obvious loose connections at an external room thermostat, thawing a frozen condensate pipe in cold weather, and trying a single boiler reset. Beyond that, any work involving the sensor wiring inside the boiler casing, the expansion vessel, the PCB, or any gas component must be carried out by a Gas Safe registered engineer. Never attempt more than two or three resets if the fault keeps returning.
How much does it cost to repair a Chaffoteaux 430 fault?
For the most common causes — a temperature sensor replacement or a pressure-related fix — most homeowners pay in the region of £120 to £350 including the engineer's call-out. A sensor and labour typically comes to £100–£200; expansion vessel work runs £100–£300. If the root cause turns out to be the PCB, the total cost including parts and labour can rise to £400 or more, and for an older boiler it is worth getting a replacement quote at the same time. Emergency call-outs outside normal working hours will add a premium of £50–£150 on top.
My Chaffoteaux boiler keeps showing 430 after I reset it — what should I do?
A fault that returns repeatedly after resetting is telling you the underlying problem has not been resolved. Repeated resets will not fix a failed sensor, a corroded connector, or a pressure fault, and some Chaffoteaux models limit the number of resets allowed for safety reasons. Stop resetting, note how quickly the code returns (immediately, after ignition, or after running for a while), and call a Gas Safe registered engineer with that information — it will help them diagnose the fault more quickly.