Intergas 8 Fault Code: Causes, Fixes & Repair Costs
What does the Intergas 8 fault code mean?
Fault code 8 on an Intergas boiler signals that the PCB has detected the fan is not running at the speed it expects. The fan plays a critical safety role: it creates the draught needed to push harmful combustion gases out through the flue. Because of this, the boiler's control board will not allow ignition to proceed until it confirms the fan is operating correctly. Importantly, the fan does not need to have stopped completely to trigger this code — even a speed that is too low to safely vent exhaust gases is enough to cause a lockout. As a precaution, the boiler will shut itself down and display fault code 8 until the issue is resolved and the appliance is reset.
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
- Fan running below required speed or failing Common
The fan itself is the most frequent culprit. Over time, the bearings inside the fan can dry out and wear, causing it to spin more slowly than the PCB requires. A fan that is running but below the minimum threshold will still trigger fault code 8 just as reliably as one that has stopped altogether. The boiler locks out as a direct safety response.
- Faulty air pressure switch Sometimes
The PCB determines whether the fan is running at the correct speed partly by reading signals from the air pressure switch. If this switch has failed or is giving erratic readings, the PCB may conclude the fan speed is wrong even when the fan itself is perfectly healthy. A blocked or split sensing tube connected to the switch can produce the same false result.
- PCB fault or poor wiring connection Rare
In some cases the issue lies with the board rather than the fan or the pressure switch. A faulty PCB may misinterpret the signals it receives, leading it to report a fan speed fault incorrectly. PCB failures are sometimes caused by component ageing, but water ingress from a leak elsewhere in the boiler — such as from the heat exchanger or pump — can also cause electrical damage that manifests as a false fault code.
How to fix it
- Check the boiler display and note the fault code DIY safe
Confirm that fault code 8 is showing on the Intergas control panel. Take a note of when the lockout occurred and whether the boiler had been running normally beforehand, as this information will help an engineer diagnose the problem more quickly.
- Do not attempt to repeatedly reset the boiler DIY safe
Intergas boilers lock out for a safety reason. Pressing the reset button once to see if the fault clears is reasonable, but continually resetting without addressing the underlying problem risks damaging other components or masking a developing issue. If the fault returns after a single reset, leave the boiler locked out.
- Call a Gas Safe registered engineer to inspect the fan and associated components Gas Safe engineer
An engineer will check the fan's actual running speed against the manufacturer's specification. If the speed is low, they may be able to adjust it; if the fan is worn or seized they will replace it. Fan bearings drying out is a recognised cause of this fault on Intergas boilers, so a thorough inspection of the fan assembly is essential.
- Engineer to test the air pressure switch and sensing tubes Gas Safe engineer
Using appropriate test equipment, the engineer will verify whether the air pressure switch is producing the correct signal when the fan runs. Blocked or cracked sensing tubes are straightforward to replace; a faulty switch itself will also need to be swapped out to clear the fault reliably.
- Engineer to inspect PCB connections and test the board Gas Safe engineer
If the fan and pressure switch check out as healthy, attention turns to the PCB. The engineer will inspect wiring connectors for corrosion or looseness and test the board with a multimeter. Where the board itself has failed — particularly if water damage is evident — replacement is usually the only lasting fix. The engineer should also identify and repair any leak that may have caused the water ingress in the first place.
Parts you may need
- Intergas boiler fan assembly · from £120
- Air pressure switch · from £35
- Pressure switch sensing tube / hose · from £8
- Printed circuit board (PCB) · from £200
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 £200–£380, depending on the underlying cause.
Frequently asked questions
Can I reset my Intergas boiler myself when fault code 8 appears?
You can try a single reset to see whether the fault clears, but do not keep resetting the boiler repeatedly. Intergas boilers lock out to prevent harm, and continually overriding the lockout without fixing the root cause risks making the problem worse. If the fault code comes back after one reset, leave the boiler off and arrange for a Gas Safe engineer to investigate.
How much does it cost to fix Intergas fault code 8 in the UK?
The most common repair is fan replacement or an air pressure switch swap, which typically costs between £200 and £380 all-in including parts and labour. Intergas also offers a fixed-price repair that covers the fan and pressure sensor together for around £239. PCB replacement is a less common but pricier outcome, often running to £400–£500 depending on the engineer and the specific board required — if this applies to you, it may be worth comparing the repair cost against a new boiler quote, especially on an older appliance.
Why does the fan cause such a serious fault on a boiler?
The flue fan creates the draught that carries toxic combustion gases — including carbon monoxide — safely out of your home through the flue. Without a fan running at the correct speed, those gases cannot be reliably expelled, creating a serious safety risk. This is why the boiler's PCB monitors fan speed continuously and locks the appliance out the moment it detects a problem, rather than allowing ignition to go ahead.
Could fault code 8 come back after the repair?
If the underlying cause has been properly identified and fixed, the fault should not return. However, if a worn fan was replaced but the air pressure switch is also borderline, or if a small leak is slowly damaging the PCB, the code could reappear. A thorough engineer will check all related components during the same visit and flag anything that looks like it may cause problems in the near future. Annual Intergas servicing is also important — it is required to maintain the manufacturer's warranty and helps catch fan and pressure switch wear before a lockout occurs.