Ferroli A07 Fault Code: Causes, Fixes & Repair Costs
What does the Ferroli A07 fault code mean?
The A07 code appears when the flue gas probe detects an excessively high temperature — typically sustained for more than around two minutes — and the boiler shuts itself down as a safety precaution. Because it begins with 'A', this is a lockout fault on Ferroli boilers, meaning the boiler will not restart on its own and needs a manual reset once the underlying problem has been addressed. You may also encounter the related codes F07 and F14 on some Ferroli models: F-prefix codes are 'blocking' faults that can clear automatically when the triggering condition resolves, whereas A07 always requires deliberate intervention. In all cases the root concern is the same — the flue gas pathway or the heat exchanger is running hotter than it should be, and the boiler is protecting itself from damage or a potentially unsafe condition.
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
- Blocked or obstructed flue terminal Common
Debris such as leaves, a bird's nest, or ice build-up at the external flue outlet can restrict the flow of combustion gases. When gases cannot escape efficiently, heat backs up inside the system and the flue temperature rises quickly. This is the first thing to rule out because it costs nothing to check from outside.
- Fan fault or reduced fan output Common
The boiler fan is responsible for drawing combustion gases safely through the heat exchanger and out of the flue. If the fan motor is wearing out, its impeller is dirty or damaged, or it is running below the correct speed, draught through the flue will be insufficient and flue gas temperatures will climb above safe limits.
- Scaled or fouled heat exchanger Common
Limescale and combustion deposits accumulate on the heat exchanger over time, particularly in hard-water areas. A heavily scaled exchanger cannot transfer heat to the water circuit efficiently, so more heat is retained in the flue gases and the probe temperature rises. This tends to develop gradually on boilers that have not had regular servicing.
- Faulty or degraded flue gas probe/sensor Sometimes
The probe that monitors flue gas temperature can drift out of calibration or develop an internal fault, causing it to report falsely high readings even when actual conditions are normal. A damaged sensor lead or a loose connection at the probe can produce the same misleading signal.
- Frozen condensate pipe Sometimes
In cold weather the external section of the condensate pipe can freeze solid, causing a back-pressure that disrupts combustion airflow and can indirectly affect flue gas temperature readings. This is worth checking any time the A07 appears during a cold snap.
- Faulty air pressure switch Sometimes
The air pressure switch confirms that the fan is generating adequate draught before allowing the burner to fire. A switch that is stuck, has a blocked sensing tube, or has failed electrically can give the control board incorrect information about flue conditions, contributing to unsafe operation and triggering the A07 lockout.
How to fix it
- Inspect the external flue terminal for visible blockages DIY safe
Go outside and look at the point where the flue exits the building. Check for bird nests, compacted debris, ice, or any physical obstruction covering the outlet. Do not attempt to access the roof unsafely; if the terminal is at height and you cannot see it clearly from ground level, leave this check to an engineer.
- Check whether the condensate pipe is frozen DIY safe
During cold weather, locate the condensate pipe — usually a white or grey plastic pipe (typically 21.5 mm or 32 mm diameter) that exits the boiler and runs to an external drain or soakaway. If it feels solid or you can see ice, gently warm the frozen section using warm (not boiling) water or a heat pad. Never use a naked flame.
- Reset the boiler once the external checks are complete DIY safe
Switch the boiler off at its power switch and leave it for around 10–15 seconds to allow the internal electronics to settle. Then press and hold the reset button while switching the boiler back on. Keep the reset button pressed until the display changes or the boiler completes its startup sequence, then release it. If the A07 returns within a short period, do not keep resetting — repeated forced restarts when a mechanical fault is present can cause costly damage to the heat exchanger or fan.
- Do not reset the boiler more than two or three times DIY safe
If the fault code reappears after two or three resets, there is a genuine internal problem. Stop attempting resets and arrange for a Gas Safe engineer to investigate. Each unnecessary restart risks overheating and damaging components.
- Have a Gas Safe engineer inspect the fan and air pressure switch Gas Safe engineer
An engineer will test fan speed and output, check the pressure switch sensing tube for blockages or cracks, and verify that the switch is opening and closing at the correct differential pressure. A faulty fan or switch will be replaced with the correct Ferroli part.
- Have the flue gas probe tested and replaced if necessary Gas Safe engineer
The engineer will measure the probe's electrical resistance and compare it against the manufacturer's specification across a range of temperatures. A probe that reads outside tolerance, or whose wiring is damaged, will be replaced. This is a straightforward repair on most Ferroli models.
- Have the heat exchanger inspected and chemically cleaned or descaled Gas Safe engineer
If servicing history is poor or the boiler is in a hard-water area, the engineer may flush or chemically descale the heat exchanger. A severely scaled exchanger that cannot be restored may need replacement — a costlier repair that, on older units, can tip the balance towards replacing the boiler altogether.
- Call a Gas Safe registered engineer if the fault persists or you are unsure Gas Safe engineer
If none of the homeowner checks resolve the A07, or if the boiler is locking out repeatedly, contact a Gas Safe registered engineer. You can verify any engineer's registration at gassaferegister.co.uk. Do not attempt to access internal gas components, the PCB, or the fan yourself.
Parts you may need
- Flue gas temperature probe/sensor · from £35
- Boiler fan/flue fan assembly · from £95
- Air pressure switch · from £30
- PCB (main control board) · from £140
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–£300, depending on the underlying cause.
Frequently asked questions
What is the difference between Ferroli fault codes A07, F07, and F14?
All three relate to abnormal flue gas temperature conditions, but they behave differently. A07 is a lockout code — the boiler shuts down completely and will only restart after a manual reset. F07 and F14 are blocking codes, meaning the boiler pauses operation but may attempt to restart automatically once the triggering condition clears (for example, if a condensate pipe thaws). If you are seeing F07 or F14 regularly, or they have progressed to A07, treat it as a sign that an underlying fault needs professional attention rather than relying on automatic recovery.
Can I reset a Ferroli A07 fault myself?
Yes, a single reset attempt is a reasonable first step once you have checked the flue terminal and ruled out a frozen condensate pipe. Switch the boiler off, wait about 15 seconds, then press and hold the reset button while turning it back on. However, if the code returns after two or three resets, stop and call a Gas Safe engineer. Repeatedly forcing the boiler to fire when a mechanical fault is present — particularly a fan or heat exchanger problem — risks causing serious and expensive damage.
How much does it typically cost to fix a Ferroli A07 fault in the UK?
Most A07 repairs fall in the region of £100–£300 all-in. A flue gas sensor replacement is usually at the lower end (roughly £80–£130 including labour), while a fan replacement typically costs £180–£250. A Gas Safe engineer's initial diagnosis visit alone generally costs £80–£150. If the heat exchanger is severely scaled and needs replacement, costs can rise considerably higher — potentially £400–£600 or more — and on a Ferroli that is over 10 years old it is worth comparing that against the cost of a new boiler.
Why does my Ferroli keep showing A07 even after a reset?
A recurring A07 almost always points to a persistent mechanical or sensor problem rather than a one-off glitch. The most common culprits are a fan that is losing efficiency, a heat exchanger that is heavily scaled and retaining too much heat, or a flue gas probe that has drifted out of calibration. Less often, a partially blocked flue terminal or a faulty air pressure switch is the cause. Each time you reset without fixing the root cause, you risk further damage, so arrange a professional inspection if the fault keeps coming back.