Intergas F027 Fault Code: Causes, Fixes & Repair Costs
What does the Intergas F027 fault code mean?
The F027 code appears on Intergas Xtreme and Xclusive boilers when the PCB detects a problem with the S6 outside weather sensor. This sensor — Intergas part 203207 — is an NTC thermistor fitted to an external wall that feeds live outdoor temperature data to the boiler, enabling weather-compensated heating control. When the PCB receives a reading that is out of range, implausible, or simply absent, it logs F027 and typically disables weather compensation. In many cases the boiler will continue to run in a reduced mode, but the fault should be investigated promptly. Importantly, if the boiler has been configured to expect an S6 sensor that was never installed or has since been removed, F027 can appear without any physical sensor being present at all.
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 degraded S6 sensor Common
The NTC thermistor inside the sensor naturally degrades over time. As it ages, it can produce resistance readings that fall outside the range the PCB considers valid, triggering F027. This is the most frequent root cause, particularly on systems that have been running for several years.
- Damaged or loose sensor wiring Common
The cable running from the outdoor sensor into the boiler is exposed to the elements and potential rodent damage. Loose terminals at either the sensor head or the boiler's PCB connector block — or corrosion along the cable run — can break the signal and cause the fault to appear even when the sensor itself is still intact.
- Boiler configured to expect a sensor that is not connected Sometimes
If a previous engineer set up the boiler's parameters to use weather compensation but the S6 sensor was never fitted, or was later removed, the PCB will flag F027 because it is looking for a signal that simply is not there. Reconfiguring the boiler parameters to disable S6 expectation clears the fault without any parts being needed.
- Incorrect sensor siting causing implausible readings Sometimes
The S6 sensor must be mounted on a north-facing wall away from direct sunlight and heat sources. If it has been placed where it receives solar gain or radiated heat from the building fabric, it can return temperature readings the PCB considers implausible, logging F027 even though the wiring and sensor are undamaged.
- PCB communication fault Rare
In rare cases the PCB itself may be unable to correctly interpret signals from the S6 circuit, either due to component failure on the board or damage to the connector block. This would typically only be suspected after the sensor and wiring have been confirmed as healthy.
How to fix it
- Check whether the S6 sensor is actually fitted to your property DIY safe
Have a look outside for a small sensor unit mounted on an external wall, usually on the north-facing elevation. If you cannot find one, it is possible the boiler has been misconfigured to expect a sensor that was never installed — note this down and mention it to the engineer.
- Do not attempt to reset the boiler repeatedly DIY safe
A single reset may temporarily clear the display, but F027 will return if the underlying sensor issue is not resolved. Pressing reset more than two or three times without fixing the fault is not recommended and will not help diagnose the problem.
- Have an engineer verify the boiler's parameter settings Gas Safe engineer
A competent heating engineer can check the boiler's configuration to confirm whether it is set to use the S6 weather sensor. If weather compensation is not required or the sensor was never fitted, the parameters can be adjusted to disable S6 monitoring, clearing the fault without any parts being replaced.
- Have the sensor wiring inspected and tested Gas Safe engineer
An engineer should carry out a visual inspection of the full cable run from the sensor to the PCB connector block, looking for corrosion, damage, or loose terminals. They can then use a multimeter to confirm continuity and check for short circuits before condemning the sensor itself.
- Have the S6 sensor resistance tested and replaced if faulty Gas Safe engineer
The S6 sensor is an NTC 12 kΩ thermistor (Intergas part 203207). An engineer can measure its resistance at a known ambient temperature and compare the reading against the expected curve. If the sensor is out of specification, it should be replaced. Because the sensor is an external component, the job is typically straightforward and does not require opening the boiler's sealed sections.
- Call a Gas Safe registered engineer if you have not already done so Gas Safe engineer
Although F027 does not directly involve the gas or combustion circuit, all boiler work in the UK must be carried out by a Gas Safe registered engineer. Contact one to diagnose and resolve the fault — given the relatively low parts cost for the S6 sensor, this is usually one of the more affordable Intergas repairs.
Parts you may need
- Intergas S6 Outside Weather Sensor (part 203207) · from £40
- Sensor cable / wiring loom (if damaged) · from £15
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–£200, depending on the underlying cause.
Frequently asked questions
Will my boiler still work with an F027 fault?
In most cases, yes. Intergas boilers displaying F027 will typically continue to provide heating and hot water, but with weather compensation disabled. The boiler reverts to a fixed flow temperature rather than adjusting dynamically to outdoor conditions, which can slightly reduce efficiency. You should still arrange for an engineer to investigate promptly rather than leaving it indefinitely.
Can I clear F027 myself by just resetting the boiler?
A reset will clear the code from the display temporarily, but F027 will come straight back once the boiler runs its next self-check if the underlying fault has not been fixed. Repeated resets are not a solution. The only permanent fix is to either correct the wiring or sensor, replace the S6 sensor, or reconfigure the boiler so it no longer expects a weather sensor — all of which require a heating engineer.
How much does it cost to fix an Intergas F027 fault?
Because the S6 sensor is an external, non-gas component, F027 is generally one of the cheaper Intergas faults to repair. The genuine Intergas S6 sensor (part 203207) costs around £35–£40 for the part alone, and fitting time is typically under an hour for an experienced engineer. Most homeowners pay in the region of £100–£200 all-in. If the fault turns out to be a PCB communication issue rather than the sensor, costs could be higher — PCB replacement on any boiler can run to several hundred pounds — but this is an uncommon cause of F027.
Does my Intergas boiler need an outside sensor?
The S6 outside sensor is an optional accessory that enables weather compensation — a feature that adjusts the boiler's flow temperature based on how cold it is outside, improving efficiency. It is not required for the boiler to operate. If weather compensation is not being used, an engineer can simply reconfigure the boiler's parameters to disable the S6 sensor input, which will clear F027 permanently without needing to purchase or fit any parts.