Intergas F011 Fault Code: Causes, Fixes & Repair Costs
What does the Intergas F011 fault code mean?
The F011 code on an Intergas boiler indicates a fault with the S0 temperature sensor, which sits at the top left of the heat exchanger. This sensor feeds live temperature data to the PCB so the boiler can monitor heat exchanger performance and respond safely to demand from your heating and hot water. When the PCB loses a valid signal from the S0 sensor — whether because the sensor itself has failed, its wiring is damaged, or a related component such as the fan is causing the fault chain to trigger — the boiler locks out and shuts down as a safety precaution. The F011 lockout will not clear permanently until the underlying cause has been identified and resolved by a Gas Safe registered engineer.
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 failed S0 sensor Common
The S0 sensor itself is the most frequent culprit. Over time, the sensor element can degrade or fail outright, causing it to send readings outside the expected range or no signal at all. The PCB interprets this as a potentially dangerous condition and locks the boiler out. Replacing the sensor is usually the first repair a Gas Safe engineer will attempt once wiring has been ruled out.
- Damaged or disconnected S0 sensor wiring Common
The wiring harness connecting the S0 sensor to the PCB can suffer from corrosion, chafing against surrounding components, or a loose plug connection. Even a partial break in the circuit can be enough to make the PCB read a fault. This is typically the first thing an engineer will check visually and with a multimeter before ordering parts.
- Fan assembly fault Sometimes
Intergas's own diagnostic guidance for F011 includes checking the fan wiring and fan assembly, which suggests the fan circuit is closely linked to the S0 fault chain. A failing fan or damaged fan wiring can contribute to or trigger the F011 code even if the sensor itself is intact. Engineers will test the fan as part of the diagnostic process.
- Faulty PCB Rare
If the wiring, sensor, and fan all check out correctly, attention turns to the PCB. The board may be misinterpreting sensor signals, or an internal failure may be generating a false F011 fault. PCB replacement is generally a last resort given the cost involved, but it is a confirmed pathway in Intergas's own guidance for this code.
How to fix it
- Check that the boiler's gas supply is turned on DIY safe
Confirm the gas isolation valve on the supply pipe to the boiler is in the open (in-line) position and that other gas appliances in the home are working. A general gas supply outage can sometimes cause unexpected lockouts. If there is no gas anywhere in the property, contact your gas supplier or call the National Gas Emergency Service on 0800 111 999.
- Attempt a single boiler reset DIY safe
Press and hold the reset button on your Intergas boiler as described in your user manual (typically holding the flame button for a few seconds until the display changes). If the boiler fires up and then displays F011 again within a short period, the fault is genuine and persisting — do not keep resetting. Repeated resets without fixing the underlying issue can cause further stress to internal components.
- Call a Gas Safe registered engineer to inspect the S0 sensor wiring and connections Gas Safe engineer
The engineer will carry out a visual inspection of the wiring loom running to the S0 sensor at the top left of the heat exchanger, checking for signs of corrosion, chafing, or disconnected plugs. They will then use a multimeter to verify electrical continuity and resistance values. This step costs nothing extra if carried out as part of the diagnostic visit and often resolves the fault without any parts being needed.
- S0 sensor replacement if wiring is intact Gas Safe engineer
If the wiring checks out but the sensor is reading outside its correct resistance range, the engineer will replace the S0 sensor. The part itself costs roughly £50, making this a relatively affordable repair. Once fitted, the engineer will clear the lockout and run the boiler through a heat cycle to confirm the fault has cleared.
- Fan assembly inspection and replacement if required Gas Safe engineer
Because Intergas's own diagnostic chain for F011 includes the fan, the engineer should also check fan wiring and run the fan to verify it operates correctly at the right speed. A faulty fan or damaged fan wiring will be repaired or the assembly replaced. A fan replacement typically costs £200–£400 including parts and labour.
- PCB replacement if all other components test satisfactory Gas Safe engineer
If the sensor, wiring, and fan all pass testing, the PCB is likely generating a false fault or has an internal failure. The engineer will confirm this diagnosis before ordering a board. PCB replacement is the most expensive pathway for this fault, so a good engineer will exhaust all other possibilities first.
Parts you may need
- S0 heat exchanger temperature sensor · from £50
- Fan assembly (Intergas Xclusive/Xtreme) · from £180
- PCB (main control board) · from £220
- Wiring harness/loom · from £35
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 reset the boiler to clear F011 myself?
You can try a single reset, but it is unlikely to clear the fault permanently. F011 is a lockout triggered by a sensor or wiring problem, and the boiler will simply lock out again once it detects the same fault condition. Resetting more than two or three times without fixing the root cause is not recommended, as it puts unnecessary strain on other components. You need a Gas Safe engineer to diagnose and repair the underlying issue.
How long do Intergas warranties last, and could my repair be covered?
Intergas boilers come with at least a 12-month standard warranty, but many models qualify for extended cover of between 3 and 10 years when registered and serviced annually by a Gas Safe engineer. If your boiler is within the warranty period and has been serviced as required, the cost of parts — and sometimes labour — may be covered. Contact Intergas Heating UK directly or check your warranty documentation before authorising any paid repair.
Are Intergas spare parts easy to get hold of in the UK?
Intergas boilers are generally well-regarded by engineers for their straightforward design, but some engineers have reported occasional delays in sourcing specific parts. Before booking a repair, it is worth asking your engineer to confirm parts availability for your exact model. The S0 sensor and fan are more commonly stocked than the PCB, which may need to be ordered. A delay in parts can extend the time your boiler is out of service, so it pays to check upfront.
What does an F011 repair typically cost in the UK, and when might it be more expensive?
For most homeowners, the repair involves either a sensor replacement or a wiring fix, and you can expect to pay in the region of £120–£380 including the engineer's callout and labour. A straightforward S0 sensor swap with a standard callout tends to sit at the lower end of that range. Fan replacement will push costs towards the higher end. If the PCB turns out to be the cause, costs can rise to £450–£600 or more depending on parts availability and your location — London and the South East tend to be 10–20% pricier than the North of England or Wales. Emergency or out-of-hours callouts add a further £120–£180 on top of the repair itself.