Intergas F012 Fault Code: Causes, Fixes & Repair Costs
What does the Intergas F012 fault code mean?
The F012 fault code appears on Intergas Xclusive and Xtreme boilers when the PCB loses a valid signal from the S5 sensor — a thermistor that continuously monitors water temperature and feeds that data back to the control board. Without a reliable reading from S5, the boiler cannot regulate heating or hot water safely, so it shuts down and displays F012. The fault is essentially the boiler saying it has lost confidence in one of its key temperature measurements; the root cause could be the sensor itself, its wiring, or — less often — the PCB that reads it.
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
- Failed or degraded S5 thermistor Common
The S5 sensor is a small thermistor that changes electrical resistance in proportion to temperature. Over time — particularly in older boilers or those that have run at high temperatures — the thermistor element can drift out of calibration or fail completely, producing a reading the PCB cannot trust. This is the single most common cause of F012.
- Loose, corroded, or damaged sensor wiring Common
The low-voltage wiring loom that connects the S5 sensor to the PCB can chafe against internal components, corrode at the connector pins, or simply work loose over years of vibration and thermal cycling. Even partial continuity loss is enough to produce an invalid signal and trigger F012.
- Faulty PCB Sometimes
If the sensor and its wiring test correctly with a multimeter, attention turns to the PCB itself. A failing control board may misinterpret or fail to read sensor signals altogether, generating F012 even though the S5 thermistor is perfectly healthy. PCB faults are less common but should be ruled out after sensor checks.
How to fix it
- Check your gas supply is working DIY safe
Before calling anyone, confirm that other gas appliances in your home — hob, gas fire — are working normally. If there is no gas supply at all, contact your gas supplier rather than a boiler engineer.
- Reset the boiler once DIY safe
Press and hold the reset button (usually marked with a flame or 'R' symbol) for a few seconds. If F012 clears and the boiler runs normally, monitor it closely. If the fault returns within a short time, do not keep resetting — a recurring F012 points to a genuine component issue that needs an engineer.
- Have a Gas Safe engineer check the S5 sensor resistance Gas Safe engineer
The engineer will use a calibrated multimeter to measure the electrical resistance of the S5 thermistor at its current temperature and compare the reading against Intergas's published resistance curve. A reading outside tolerance confirms a faulty sensor.
- Have the engineer inspect the sensor wiring loom Gas Safe engineer
The wiring between the S5 sensor and the PCB connector will be checked for signs of corrosion, chafing, or loose terminals. Any damaged section of the loom will be repaired or replaced before retesting.
- Replace the S5 thermistor if confirmed faulty Gas Safe engineer
Thermistors are relatively inexpensive parts. If the resistance test shows the sensor is out of specification, swapping it is a straightforward job for a qualified engineer and resolves the vast majority of F012 faults.
- Replace the PCB if sensor and wiring are both serviceable Gas Safe engineer
When the S5 sensor and its wiring both pass inspection, the PCB is the remaining suspect. The engineer will verify the board is receiving and processing signals correctly; if it is not, a PCB replacement will be required. This is the costlier repair path.
- Call a Gas Safe registered engineer if you have not already done so Gas Safe engineer
All work beyond the basic reset described above must be carried out by a Gas Safe registered engineer. You can verify any engineer's registration at gassaferegister.co.uk. Do not attempt to access internal boiler components yourself.
Parts you may need
- S5 thermistor (NTC temperature sensor) · from £18
- Sensor wiring loom / harness · from £35
- Intergas PCB (Xclusive / Xtreme) · 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–£350, depending on the underlying cause.
Frequently asked questions
Can I reset my Intergas boiler to clear F012 myself?
You can try a single reset — hold the reset button until the boiler attempts to restart. If F012 disappears and does not return, the fault may have been a one-off glitch. However, if the code comes back after one or two resets, stop resetting and call a Gas Safe engineer. Repeated resets without fixing the underlying cause will not help and could mask a developing fault.
How much does it cost to fix an Intergas F012 fault?
For most people the bill lands somewhere between £120 and £350, covering the call-out, diagnosis, and a sensor or wiring repair. The S5 thermistor itself is an inexpensive part — typically under £25 — so labour is the main cost. If the PCB turns out to be the culprit, the part alone can cost £180–£300, pushing the total repair closer to £400–£500. If your boiler is over ten years old and the PCB needs replacing, it is worth comparing the repair cost against a new boiler.
What is the S5 sensor on an Intergas boiler and where is it located?
The S5 sensor is a thermistor — a resistor whose electrical resistance changes predictably with temperature. The boiler's PCB reads this resistance thousands of times per hour to know the current water temperature and adjust the burner accordingly. On Intergas Xclusive and Xtreme models it is mounted on the hydraulic block or flow pipework inside the boiler casing. Its exact position is model-specific, which is another reason internal inspection should only be carried out by a qualified engineer.
Will an Intergas warranty cover an F012 fault?
Intergas boilers come with a standard 12-month warranty, and depending on the model and whether it was professionally installed and serviced, cover can extend to three or ten years. If your boiler is within its warranty period, contact Intergas or your installer before arranging an independent repair — using an unauthorised engineer for warranty work can sometimes invalidate the remaining cover. Keep your annual Gas Safe service records as proof of maintenance.