Intergas 27 Fault Code: Causes, Fixes & Repair Costs
What does the Intergas 27 fault code mean?
Fault code 27 on an Intergas boiler is an engineer-level diagnostic code that sits outside the small number of codes Intergas publishes in its consumer-facing documentation. Based on the Intergas fault code structure — where codes in the teens and twenties typically relate to sensor readings, secondary safety functions, or component-level faults — code 27 most likely indicates that the boiler's control board has detected an abnormal reading from a temperature sensor, the fan circuit, or a secondary safety device, and has locked the boiler out as a precaution. Because this code is not listed in standard user manuals, a Gas Safe registered engineer with Intergas experience should be contacted to confirm the exact diagnosis using Intergas diagnostic software or the full technical documentation.
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 disconnected temperature sensor (S1 or S2) Common
Intergas boilers rely heavily on two key temperature sensors — S1 and S2 — to monitor flow and return temperatures. If either sensor has developed a fault, lost its connection, or drifted outside its expected resistance range, the PCB will raise a lockout code in the 20s range. This is the most frequently reported cause for higher-numbered Intergas fault codes.
- Fan circuit fault or incorrect fan speed Common
The fan is responsible for expelling combustion gases through the flue. If the fan is running too slowly, not at all, or the tachometer signal feeding back to the PCB is erratic, the boiler will lock out to prevent unsafe combustion conditions. Codes in the 20s on Intergas boilers can reflect this kind of fan-related safety trip.
- Wiring harness damage or loose connection Sometimes
Vibration, age, or poor workmanship during a previous service can leave sensor or fan wiring partially disconnected or chafed against the casing. A loose plug on a sensor or fan lead can mimic a component failure and trigger a lockout code without the underlying component actually being faulty.
- PCB (printed circuit board) failure Sometimes
If the control board itself is misreading sensor data or has an internal fault, it can generate diagnostic codes that do not correspond to a genuine component failure. PCB faults are less common but should be considered once sensors, wiring, and the fan have been eliminated.
- Overheat or circulation fault Sometimes
Poor water circulation — caused by a sluggish pump, a partially blocked heat exchanger, or an airlock — can drive temperatures beyond safe limits and trigger a safety lockout. The boiler may display a higher-numbered code to indicate which safety threshold was exceeded.
How to fix it
- Check the boiler's system pressure DIY safe
Look at the pressure gauge on the front of the boiler. It should read between 1 and 1.5 bar when the system is cold. If it has dropped below 1 bar, top it up via the filling loop until it reaches 1.2–1.5 bar, then attempt a reset. Low pressure alone can sometimes cause spurious fault codes.
- Attempt a boiler reset — but no more than twice DIY safe
Press and hold the key (reset) button on the boiler until the fault code clears. Wait for the boiler to complete its ignition sequence. If the code returns immediately or after a short run, do not keep resetting — repeated resets on a persistent fault can mask a worsening problem and may void your warranty.
- Check that the gas supply to the property is on DIY safe
Confirm that other gas appliances (hob, gas fire) are working normally. If there is a gas supply problem, contact your gas supplier. If other appliances work fine, the issue is specific to the boiler.
- Visually inspect the flue terminal from ground level DIY safe
From outside, check whether the flue outlet is visibly blocked by debris, a bird nest, or ice. Do not climb ladders or go onto the roof. If you can safely clear an obvious blockage from the ground, do so, then reset the boiler.
- Check that all radiator valves are open and bleed radiators if needed DIY safe
If radiator valves are closed or radiators have airlocks, circulation is restricted and the boiler can overheat. Open all thermostatic radiator valves fully and bleed any radiators that feel cold at the top to remove trapped air.
- Call a Gas Safe registered engineer to diagnose the fault Gas Safe engineer
Because fault code 27 is an engineer-level code not published in Intergas consumer documentation, a Gas Safe engineer familiar with Intergas boilers is required to confirm its exact meaning. Ask them to bring the Intergas diagnostic interface cable or use Intergas Software Diagnostics to read live data from the PCB. They will check S1 and S2 sensor resistances, inspect the fan and its tachometer signal, test the wiring harness for continuity, and confirm whether the PCB itself needs attention.
Parts you may need
- Intergas S1/S2 temperature sensor (NTC thermistor) · from £25
- Intergas fan assembly · from £120
- Intergas PCB (control board) · from £220
- Intergas pump · from £85
- Wiring harness / sensor loom · from £40
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
Why is Intergas fault code 27 not in my boiler manual?
Intergas publishes only a small number of codes — primarily 1 through 11 — in its consumer-facing operating instructions. Codes in the twenties and above are engineer-level diagnostic codes that appear in the full technical documentation rather than the homeowner manual. This does not mean the fault is more serious by default; it simply means it needs a trained engineer to interpret correctly using the complete fault code reference and, where appropriate, Intergas diagnostic software connected to the boiler's PC interface.
Can I reset my Intergas boiler to clear code 27?
You can try a reset once or twice by pressing and holding the key button on the boiler. However, if the code returns after resetting, do not keep trying — repeated resets will not fix the underlying fault and could mask a developing problem. Code 27 is a lockout code, meaning the boiler has shut down deliberately for safety. A Gas Safe engineer should investigate the root cause before the boiler is returned to normal use.
How much will it cost to fix Intergas fault code 27 in the UK?
For the most common causes — a faulty temperature sensor or a wiring issue — most people pay between £120 and £250 including the engineer's call-out, parts, and labour. If the fan needs replacing the bill typically rises to around £250–£380. In less common cases where the PCB has failed, costs can reach £400–£500 or more, but this is the exception rather than the rule. Always ask for a written quote before work begins.
Will fault code 27 affect my Intergas warranty?
Intergas boilers come with a standard 12-month warranty, extendable to between 3 and 10 years on some models when registered and serviced annually by a Gas Safe engineer. Having the fault repaired by a qualified Gas Safe engineer who uses genuine Intergas parts will protect your warranty. Attempting DIY repairs or using non-approved parts could invalidate it. If your boiler is still within the warranty period, contact Intergas's UK support line before booking an independent engineer, as the repair may be covered.