Ariston 607 Fault Code: Causes, Fixes & Repair Costs
What does the Ariston 607 fault code mean?
Fault code 607 on an Ariston boiler means the air pressure switch has registered a closed (active) state before the fan has even started up. In normal operation, the fan runs first to clear the flue, and only once it has built up sufficient draught does the pressure switch close to confirm everything is safe. When the boiler detects the switch is already closed at the point it should be open — before ignition has begun — it locks out and displays 607 as a flue-gas safety precaution. The most consistent cause is a problem in the fan, flue, or pressure-sensing circuit, though in some cases a wiring fault or PCB communication issue can produce the same code.
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
If the flue outlet on the outside wall is partially or fully blocked — by a bird's nest, debris, compacted snow, or a nearby obstruction — the fan cannot create the correct pressure differential. The pressure switch may then behave erratically, triggering the 607 lockout before ignition even attempts.
- Faulty or non-running fan Common
The fan (also called the flue gas extractor or combustion fan) may have failed outright, be running at the wrong speed, or have seized bearings. Because the fan is responsible for venting combustion gases safely, the boiler locks out immediately if it suspects the fan is not functioning correctly.
- Split, kinked, or disconnected pressure switch tube Common
A short rubber or silicone hose connects the fan/flue assembly to the air pressure switch. If this tube develops a crack, becomes kinked, or has slipped off its spigot, the switch cannot read the correct pressure and may falsely indicate a pre-ignition trip.
- Faulty air pressure switch Sometimes
The air pressure switch itself can fail mechanically or electrically. A switch that is stuck in the closed position will cause the boiler to detect an active signal before the fan runs, producing the 607 code even when the fan and flue are perfectly healthy.
- Wiring fault or loose PCB connection Sometimes
Vibration or age can loosen the wiring between the PCB and the air pressure switch. A loose or corroded connector can send a false signal to the PCB, causing it to believe the switch has tripped prematurely. In most cases this is a straightforward fix, but the engineer must rule out deeper PCB damage, particularly if water ingress has occurred.
- PCB fault Rare
In rarer cases, the PCB itself misinterprets signals from the pressure switch circuit due to component failure or water damage. The boiler locks out as a precaution. PCB faults tend to produce intermittent or hard-to-replicate errors alongside 607, and are typically diagnosed only after other components have been ruled out.
How to fix it
- Check the external flue terminal for obstructions DIY safe
Go outside and visually inspect the flue terminal on the external wall. Look for a bird's nest, leaves, snow, ice, or any physical obstruction covering or partially blocking the outlet. Do not poke anything into the flue terminal. If you can safely clear surface debris (such as brushing away snow), do so, but do not attempt to dismantle any part of the flue.
- Attempt a single boiler reset DIY safe
On most Ariston models, press and hold the reset button for approximately five seconds. Allow the boiler to complete its start-up sequence. If it runs normally, monitor it closely over the next 24–48 hours. If fault code 607 returns straight away or after only a short time, do not keep resetting — repeated resets without an underlying fix can mask a genuine safety issue and should be avoided.
- Check system pressure is within the normal range DIY safe
While not a direct cause of 607, it is worth confirming your boiler's pressure gauge reads between 1.0 and 1.5 bar when the system is cold. If it is below 1.0 bar, top up via the filling loop according to your boiler's user guide. This rules out any secondary faults before an engineer visits.
- Have a Gas Safe engineer test the fan Gas Safe engineer
An engineer will check whether the fan is spinning freely, running at the correct speed, and generating adequate pressure in the flue circuit. A failed or slow fan is one of the most frequent causes of 607 and will require either repair or full replacement.
- Have the pressure switch tube inspected Gas Safe engineer
The engineer will examine the rubber or silicone hose running from the fan housing to the air pressure switch. They will look for splits, blockages, or loose connections and replace the tube if necessary — this is typically a low-cost repair if caught early.
- Have the air pressure switch tested and replaced if faulty Gas Safe engineer
Using a multimeter and pressure test equipment, the engineer will confirm whether the switch is opening and closing at the correct pressure thresholds. A faulty switch stuck in the closed position will need to be replaced with the correct Ariston-compatible part.
- Have PCB wiring and connections checked Gas Safe engineer
If the fan, tube, and pressure switch all test correctly, the engineer will inspect the wiring harness and PCB connectors associated with the pressure switch circuit. Loose or corroded terminals can be re-seated or replaced. If the PCB itself is damaged — particularly where water ingress is evident — replacement will be discussed.
- Call a Gas Safe registered engineer if the fault persists or you are unsure Gas Safe engineer
Fault code 607 involves the flue safety circuit, meaning combustion gases could potentially be at risk if the boiler is operated with an underlying fault. If a single reset and a quick flue check have not resolved the issue, do not continue using the boiler. Contact a Gas Safe registered engineer to carry out a full diagnosis. You can verify any engineer's registration at gassaferegister.co.uk.
Parts you may need
- Ariston air pressure switch · from £45
- Pressure switch sensing tube (rubber/silicone hose) · from £12
- Ariston flue fan / combustion fan assembly · from £130
- PCB wiring harness connector set · from £20
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–£375, depending on the underlying cause.
Frequently asked questions
Is it safe to keep using my Ariston boiler while fault code 607 is showing?
No. Fault code 607 relates to the flue safety circuit, which is there to ensure combustion gases are being safely expelled from your home. The boiler locks out specifically to prevent operation under unsafe conditions. You should not attempt to override repeated lockouts by resetting the boiler multiple times. Turn the boiler off and arrange for a Gas Safe registered engineer to inspect it before using it again.
Can I fix Ariston fault code 607 myself?
A homeowner can safely check the external flue terminal for visible obstructions (such as a bird's nest or snow) and attempt a single reset. Beyond that, the fault involves components — the fan, air pressure switch, pressure tube, and potentially the PCB — that must be diagnosed and repaired by a Gas Safe registered engineer. Working on these parts without registration is illegal and potentially dangerous.
How much does it cost to fix fault code 607 on an Ariston boiler?
Most people with a 607 fault pay somewhere between £120 and £375 all-in, depending on which component needs attention. A pressure switch tube replacement or a loose wiring fix sits at the lower end, while a full fan replacement typically costs £225–£375 including parts and labour. If the PCB needs replacing, costs can rise to £400–£500 or more, which on an older boiler may make a new boiler quotation worth considering alongside the repair estimate.
Why does my Ariston boiler keep showing 607 after I reset it?
If the fault code returns quickly after a reset, it means the underlying cause has not gone away. This is a strong sign that a physical component — most likely the fan, air pressure switch, or pressure tube — has genuinely failed and needs attention from a Gas Safe engineer. Repeated resetting without a fix is not recommended, as it bypasses the boiler's own safety lockout without addressing the reason it locked out in the first place.