Intergas F015 Fault Code: Causes, Fixes & Repair Costs
What does the Intergas F015 fault code mean?
The F015 code on Intergas Xclusive and Xtreme boilers indicates that the PCB has detected a problem with the physical mounting or positioning of the S1 sensor — the flow temperature sensor located on the heat exchanger. Rather than pointing to an electrical failure within the sensor itself (that would be F031), F015 specifically flags that the sensor appears to have lost proper thermal contact with its mounting pocket, is sitting incorrectly, or has become dislodged. Without a reliable temperature reading from the flow circuit, the boiler locks out to prevent unsafe operation. An engineer will need to inspect the sensor's position, connections, and condition before the boiler can run again.
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
- S1 sensor dislodged or poorly seated Common
This is the most common trigger for F015 specifically. Over time the sensor clip or capillary can loosen, pulling the sensor away from its pocket on the heat exchanger. With poor thermal contact, the PCB receives an unreliable or out-of-range temperature reading and shuts the boiler down. Re-seating the sensor correctly will often clear the fault without any parts being replaced.
- Wiring or connector fault to the S1 sensor Sometimes
Corroded, loose, or damaged wiring between the S1 sensor and the PCB can cause signal errors that the boiler interprets as a mounting or positioning problem. An engineer will check the harness and connectors with a multimeter and replace any defective sections.
- Limescale or sludge affecting sensor contact Sometimes
In hard-water areas, scale build-up around the sensor pocket can prevent the sensor from seating flush, effectively mimicking a mounting fault. System sludge can have a similar insulating effect. A power flush and scale inhibitor treatment may be recommended alongside any sensor work.
- PCB fault Rare
If the PCB is misreading or failing to correctly process the S1 sensor signal, it can generate a false F015 code even when the sensor itself is fine. PCB faults are less common but should be considered once the sensor, its mounting, and all wiring have been ruled out.
How to fix it
- Check your boiler's warranty status before spending anything DIY safe
Intergas boilers come with a standard 12-month warranty, and depending on the model and installer registration, this can extend to 3–10 years. If your boiler is still within warranty, contact Intergas or your installer first — the repair may be covered at no cost to you.
- Do not attempt to open the boiler casing or touch internal components Gas Safe engineer
F015 requires hands-on access to the heat exchanger and sensor pocket inside the boiler. This is not a homeowner task. Working on internal boiler components without Gas Safe registration is both illegal and potentially dangerous.
- Attempt a single boiler reset to see if the fault clears DIY safe
On Intergas boilers the reset button is on the front panel. Press and hold as described in your user guide. If the boiler fires and runs normally, monitor it closely over the next hour. If the F015 code returns, do not keep resetting — move on to calling an engineer.
- Contact a Gas Safe registered engineer to inspect the S1 sensor mounting Gas Safe engineer
The engineer will remove the boiler casing, locate the S1 flow temperature sensor on the heat exchanger, and check whether it has moved out of its pocket. In many F015 cases, simply re-seating and securing the sensor restores normal operation without any parts being needed.
- Engineer to test sensor resistance and wiring with a multimeter Gas Safe engineer
Once the physical mounting has been checked, the engineer will measure the sensor's resistance at a known temperature and compare it to the manufacturer's specification. They will also inspect the wiring harness and connectors for corrosion or damage and replace any defective components.
- Engineer to replace the S1 sensor if it is faulty Gas Safe engineer
If testing confirms the sensor itself has failed, a replacement S1 flow temperature sensor is a relatively straightforward and affordable fix — parts typically cost around £50. The engineer will fit the new sensor, ensure it is correctly secured in its mounting pocket, and clear the fault code.
- Engineer to assess and replace the PCB if all other components test correctly Gas Safe engineer
If the sensor, its mounting, and all associated wiring are confirmed good but F015 persists, the PCB is the likely culprit. PCB replacement on Intergas boilers typically costs £400–£500 including parts and labour and should only be considered once simpler causes have been eliminated.
Parts you may need
- Intergas S1 flow temperature sensor · from £50
- Sensor wiring harness / connector · from £25
- Intergas PCB (model dependent) · from £280
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–£300, depending on the underlying cause.
Frequently asked questions
What is the difference between Intergas fault codes F015 and F031?
Both codes relate to the S1 flow temperature sensor, but they mean different things. F015 is a mounting fault — the sensor has lost proper contact with its pocket on the heat exchanger, or is physically dislodged. F031 is an electrical fault — the sensor's resistance is outside the expected range, indicating the sensor itself has likely failed. F015 can sometimes be resolved simply by re-seating the sensor, whereas F031 more often requires the sensor to be replaced.
Can I reset my Intergas boiler to clear the F015 code myself?
You can try a single reset using the button on the front panel. If the boiler fires up and stays running, keep an eye on it for the next hour or so. However, F015 is a lockout code caused by an internal sensor issue, so a reset alone is unlikely to fix the underlying problem. If the fault returns — which it usually will — stop resetting and call a Gas Safe registered engineer. Repeated resets without addressing the root cause will not help and could mask a developing problem.
How much does it typically cost to fix an Intergas F015 fault?
Most people with this fault pay somewhere between £120 and £300 all in. If the fix is simply re-seating a dislodged sensor, costs are at the lower end once you factor in the call-out and labour. A full sensor replacement including parts and labour usually comes to around £120–£200. If the PCB turns out to be the cause, expect to pay £400–£500 for parts and labour — but this is far less common and only diagnosed once everything else has been ruled out.
Is my Intergas boiler still under warranty for an F015 fault?
It depends on your model and when it was installed. All Intergas boilers come with a minimum 12-month warranty, and many models carry extended cover of 3–10 years when the installation is registered. Check your paperwork or contact Intergas directly before booking a repair — if you are within the warranty period, the sensor replacement or other work may be covered at no charge. You can verify engineer credentials at any time via the Gas Safe Register at gassaferegister.co.uk.