Intergas Fault Code 6: Flame Detection Error
Fault code 6 on an Intergas boiler indicates a flame detection problem. The boiler's PCB (printed circuit board) is either expecting to see confirmation of a stable flame and not receiving it, or it is detecting a flame signal at a time when it shouldn't be. In practical terms, this usually means the burner is struggling to ignite and hold a flame, or the sensor responsible for confirming ignition is failing to report correctly. The boiler will typically lock out and refuse to operate until the underlying fault is resolved and the unit is reset.
General guidance only — not a substitute for professional advice. 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.
What does the Intergas 6 fault code mean?
Fault code 6 on an Intergas boiler indicates a flame detection problem. The boiler's PCB (printed circuit board) is either expecting to see confirmation of a stable flame and not receiving it, or it is detecting a flame signal at a time when it shouldn't be. In practical terms, this usually means the burner is struggling to ignite and hold a flame, or the sensor responsible for confirming ignition is failing to report correctly. The boiler will typically lock out and refuse to operate until the underlying fault is resolved and the unit is reset.
Common causes
- Faulty or dirty flame sensor (ionisation probe) Common
The flame sensor sends a signal to the PCB confirming a stable flame is present after ignition. Over time the sensor tip can become coated in residue, weakening the signal and causing the PCB to believe no flame has been established even when one has. A failed sensor gives the same result. This is the most frequently identified cause of fault code 6 on Intergas boilers.
- Ignition electrode or lead failure Common
The electrode creates the spark that ignites the gas, and the ignition lead carries the high-voltage pulse to it. If either component has cracked, corroded, or deteriorated, the spark may be too weak or inconsistent to reliably light the burner — producing a flame detection fault because no flame ever establishes itself properly.
- Gas valve fault Sometimes
The gas valve controls the flow of gas into the burner. If it sticks partially closed, insufficient gas reaches the burner and the flame either fails to light or is too weak to be detected. In rarer cases a valve can stick partially open, introducing gas at the wrong moment. Both scenarios can trigger fault code 6 and represent a potential safety concern.
- PCB fault Rare
The PCB coordinates ignition sequencing and interprets sensor signals. If the board itself is malfunctioning — due to a failed component, moisture ingress, or age-related deterioration — it may misread or fail to process the flame sensor signal, causing a spurious fault code 6 even when the burner hardware is in good order.
How to fix it
- Check that your gas supply is working DIY safe
Before assuming a boiler fault, confirm gas is reaching your property. Check whether your gas hob or other gas appliances are working normally. If there is no gas supply at all, contact your gas supplier rather than a boiler engineer.
- Attempt a single boiler reset DIY safe
Locate the reset button on your Intergas boiler (typically a button or dial on the front panel — refer to your user guide). Hold it for the duration specified in your manual. Because fault code 6 can have a gas-related cause, limit yourself to one reset attempt. If the fault returns promptly, do not keep resetting — repeated attempts will not resolve an underlying fault and could mask a safety issue.
- Do not attempt to inspect or clean internal components yourself Gas Safe engineer
The flame sensor, ignition electrode, ignition lead, and gas valve are all internal boiler components. Accessing or adjusting them without Gas Safe registration is both illegal for gas-related parts and potentially dangerous. Leave all internal inspection to a qualified engineer.
- Contact a Gas Safe registered engineer to test the flame sensor Gas Safe engineer
An engineer will use appropriate test equipment to check whether the ionisation probe is producing a usable signal. If the sensor is coated in deposits it may be cleaned; if it has failed it will need replacing. This is usually the first component tested given how frequently it is responsible for this fault code.
- Have the engineer inspect the ignition electrode and lead Gas Safe engineer
If the flame sensor tests satisfactorily, the engineer will check the electrode for cracking, corrosion, or incorrect gap, and test the ignition lead for continuity and insulation breakdown. Either or both components may need replacing.
- Have the engineer assess the gas valve Gas Safe engineer
All gas valve work must be carried out by a Gas Safe registered engineer. The engineer will check whether the valve is opening correctly and delivering the right gas pressure to the burner. Valves that are sticking or failing to open fully will generally need to be replaced rather than repaired, as this is the safer and more reliable outcome.
- Have the PCB tested if other components check out Gas Safe engineer
If the flame sensor, electrode, lead, and gas valve are all found to be in working order, the engineer will test the PCB using a multimeter to verify it is correctly sending and receiving signals. PCB repairs are sometimes possible on the spot, but a replacement board may be recommended if the fault is board-level.
- Call a Gas Safe registered engineer to carry out all repairs Gas Safe engineer
Given that fault code 6 can involve a gas valve fault, this is not a boiler error that should be left unattended or repeatedly reset in the hope it self-resolves. Book a Gas Safe registered engineer to diagnose and fix the fault. You can verify any engineer's registration at the Gas Safe Register website (gassaferegister.co.uk).
Parts you may need
- Intergas ionisation/flame sensor probe · from £35
- Ignition electrode · from £25
- Ignition lead (HT lead) · from £20
- Gas valve (Intergas compatible) · from £150
- Replacement PCB · from £220
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
Is it safe to keep resetting my Intergas boiler when fault code 6 appears?
No — and this is more important with fault code 6 than with many other fault codes. Because this error can indicate a gas valve problem as well as a sensing issue, repeatedly resetting the boiler is not advisable. Limit yourself to a single reset attempt. If the fault reappears, switch the boiler off and arrange for a Gas Safe registered engineer to investigate promptly.
How much does it cost to fix Intergas fault code 6 in the UK?
For the most common repairs — cleaning or replacing the flame sensor, or swapping the ignition electrode and lead — you would typically pay in the region of £120 to £220 including labour. A gas valve replacement usually comes to around £300 all in. If the PCB is to blame, expect to pay £400–£500 for parts and labour, which is at the higher end of boiler repairs. If your engineer finds that multiple expensive components are failing simultaneously, it is worth asking them to compare the repair cost against a new boiler installation.
Can a Gas Safe engineer just clean the flame sensor rather than replace it?
Yes, in many cases an engineer will clean the ionisation probe as a first step — carbon or oxide deposits on the sensor tip are a common cause of weak signals. If cleaning restores a reliable signal during testing, no replacement is needed. However, if the probe has physically failed or cleaning does not resolve the fault, replacement is the correct course of action.
Will an annual Intergas service help prevent fault code 6?
Yes. During a service, a Gas Safe engineer will inspect and clean the flame sensor, check the ignition components, and verify correct gas pressure and valve operation — all of the areas most likely to cause fault code 6. Keeping up with annual servicing also maintains your Intergas warranty, which may cover certain component failures and significantly reduce your out-of-pocket repair costs.