Chaffoteaux 406 Fault Code: Causes, Fixes & Repair Costs
What does the Chaffoteaux 406 fault code mean?
Fault code 406 appears on Chaffoteaux Talia, Talia Green, and Talia Green System boilers and signals a problem with the combustion fan subsystem. The boiler's PCB monitors fan speed during every start-up sequence — it signals the fan to run, waits for the air pressure switch to confirm that sufficient flue draught is being created, and only then opens the gas valve. Code 406 means the PCB has detected that the fan is either running below its required speed threshold or cannot verify a valid speed signal from the fan at all. As a safety measure the boiler locks out rather than attempt ignition without confirmed airflow. The '4xx' series on Chaffoteaux boilers consistently points to fan, combustion air, or related communication faults, so any code in this range — 401 through 407 — should be treated as a flue or fan issue until proven otherwise.
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
- Worn or seized fan motor Common
Over time the fan motor bearings deteriorate or the windings burn out, preventing the impeller from reaching the RPM the PCB expects to see. This is the single most common root cause of a 406 lockout and usually means the fan assembly needs replacing.
- Blocked or dirty fan impeller Common
Dust, fluff, and debris accumulate on the impeller blades, adding enough resistance to slow the fan below its minimum speed threshold. In some cases a thorough clean by an engineer restores normal operation without needing a replacement part.
- Faulty or blocked air pressure switch Sometimes
The air pressure switch sits between the fan and the PCB, physically confirming that the fan is generating adequate draught. A clogged membrane, cracked connecting tube, or corroded contacts can prevent the confirmation signal from reaching the PCB even when the fan itself is running perfectly — causing a spurious 406 lockout.
- Blocked or partially obstructed flue terminal Sometimes
A bird's nest, ice build-up in freezing weather, or debris at the external flue terminal restricts airflow and prevents the fan from achieving the draught pressure the switch is set to detect. Always worth a visual check outside before calling an engineer.
- Wiring fault between fan, pressure switch, and PCB Sometimes
A loose connector, chafed wire, or corroded terminal anywhere in the signal path from the fan tachometer or pressure switch back to the PCB can break the speed feedback loop and trigger a 406 without there being anything mechanically wrong with the fan itself.
- PCB failure Rare
In rare cases a sustained fan fault — particularly where the motor has been drawing excessive current — can damage the PCB itself. The PCB then fails to process the fan signal correctly even after the underlying mechanical fault is resolved. PCB failure on its own as a first cause of 406 is uncommon.
How to fix it
- Reset the boiler once DIY safe
Locate the reset button on your Chaffoteaux boiler (refer to your user guide for its position), press and hold it briefly, then wait a full minute for the boiler to attempt a restart. A single reset is acceptable. If the 406 code returns immediately or after one or two heating cycles, stop resetting — repeated resets without fixing the underlying fault will not help and may mask the fault history an engineer needs.
- Inspect the external flue terminal for obvious blockages DIY safe
Go outside and look at where the flue exits the building. Check for a bird's nest, leaves, ice, or any debris covering or partially blocking the terminal grille. Do not insert anything into the flue or attempt to dismantle it — simply note what you can see and report it to your engineer.
- Check the condensate pipe for freezing (cold-weather faults only) DIY safe
If the fault has appeared during a cold snap, locate the white plastic condensate pipe that exits through an outside wall or runs to an external drain. If it is frozen solid, you can carefully thaw it by pouring warm (not boiling) water along its length or wrapping it with a warm cloth. Once thawed, reset the boiler. Although a frozen condensate pipe more typically produces a different fault code, an extreme freeze event can affect draught and fan performance simultaneously.
- Gas Safe engineer: inspect and test the fan assembly Gas Safe engineer
A qualified engineer will power up the boiler in diagnostic mode to observe whether the fan starts and reaches its target RPM. They will remove the fan, clean the impeller of any dust or debris, check that the shaft rotates freely, and assess the condition of the bearings. If the motor is burnt out or the bearings are beyond reconditioning, the fan assembly will be replaced with a compatible part.
- Gas Safe engineer: test the air pressure switch and connecting tubes Gas Safe engineer
The engineer will remove the pressure switch and inspect the rubber or silicone tubes for cracks, blockages, or poor connections. They will blow through the tubes to clear any condensate or debris, listen for audible clicks confirming the switch membrane is operating, and use a multimeter to check switch contacts under simulated pressure conditions. A faulty pressure switch is replaced as a unit.
- Gas Safe engineer: check all wiring and connectors in the fan circuit Gas Safe engineer
The engineer will trace the wiring loom from the fan tachometer output and pressure switch through to the PCB, checking each connector for corrosion, looseness, or damage. A wiring repair or connector replacement is a relatively quick fix if the fan and pressure switch are otherwise healthy.
- Gas Safe engineer: evaluate the PCB if all other components check out Gas Safe engineer
If the fan, pressure switch, flue, and wiring all test satisfactorily, the PCB is likely at fault. The engineer will test PCB outputs and, if necessary, fit a replacement. On a boiler that is eight years old or more, the engineer should also advise on whether the cost of a new PCB is justified compared with investing in a new boiler installation.
Parts you may need
- Fan assembly (Talia / Talia Green range) · from £160
- Air pressure switch · from £35
- Fan motor (replacement motor only, where available) · from £65
- PCB (main printed circuit 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–£380, depending on the underlying cause.
Frequently asked questions
Can I keep resetting my Chaffoteaux boiler to clear fault code 406?
One reset is fine and worth trying — occasionally a momentary speed dip caused by a voltage fluctuation or a piece of debris temporarily catching the impeller will self-clear. However, if the 406 returns after one or two restarts, stop. The boiler is locking out for a genuine safety reason: it will not light without confirmed airflow, and repeated resets do not address the underlying fault. Call a Gas Safe registered engineer for a proper diagnosis.
How much does it cost to fix a Chaffoteaux 406 fault code?
For the two most common repairs — fan cleaning or fan replacement — most homeowners pay between £120 and £380 including parts and labour. A fan clean alone (where the motor is still serviceable) typically comes in at the lower end. A full fan assembly replacement tends to fall in the £200–£380 range depending on the engineer's call-out rate and the specific Talia model. An air pressure switch swap is usually cheaper, around £80–£150 all-in. If the PCB has been damaged as a result of the fan fault, replacement costs can rise to £400–£600 — in that situation, on an older boiler, it is worth getting a new boiler quote at the same time for comparison.
Is fault code 406 dangerous — do I need to leave my home?
Fault code 406 causes the boiler to lock out before any ignition attempt, so there is no risk of incomplete combustion or carbon monoxide production from this fault in isolation. You do not need to leave your home. That said, you should not attempt to bypass the lockout or tamper with the fan or flue yourself. Leave the boiler locked out, keep the area around the flue clear, and arrange for a Gas Safe engineer to inspect it.
My Chaffoteaux Talia is 10–12 years old and has a 406 fault. Should I repair or replace it?
Chaffoteaux condensing boilers typically last 10–15 years with good servicing. If the fault is isolated to the fan or air pressure switch and the rest of the boiler is in good condition, repair is usually worthwhile. However, if the PCB also needs replacing, or if this is the second or third significant repair in recent years, the total cost can approach — or exceed — a contribution towards a new boiler installation. Ask your Gas Safe engineer for an honest assessment of the boiler's overall condition before committing to an expensive component repair on an older unit.