Alpha 0A8 Fault Code: Causes, Fixes & Repair Costs
What does the Alpha 0A8 fault code mean?
The 0A8 fault code on an Alpha boiler indicates that the boiler attempted to light the burner but failed to establish a flame, causing the boiler to lock itself out as a safety measure. This code sits within Alpha's ignition-failure family alongside codes such as E1 and 0A1 — all of which point to a breakdown somewhere in the ignition sequence. The boiler will not restart automatically; a manual reset is required once the underlying cause has been identified. On models with a digital display the code appears as 0A8, while some older Alpha models signal ignition faults through a combination of flashing LED indicators (typically both the red 'A' and yellow 'B' lights flashing together) rather than a numeric code.
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 degraded ignition electrodes Common
The ignition electrodes are the components that generate the spark to light the burner. Over time they can wear, crack, or become coated in residue, preventing a reliable spark. Misalignment — even by a small margin — is also enough to stop ignition entirely. This is the single most common root cause of an 0A8 lockout.
- Gas supply interruption or low gas pressure Common
If the gas supply to the boiler is interrupted — because a meter has run out of credit, a gas isolation valve has been accidentally closed, or there is a temporary supply issue from the network — the boiler will attempt to fire, find no gas, and lock out. Low line pressure at the meter can have the same effect even when gas is technically available.
- Flame sensor (ionisation probe) dirty or faulty Common
The flame sensor monitors whether a flame is actually present after the spark fires. If it is coated in oxidisation or carbon deposits, it cannot detect the flame reliably and the boiler assumes ignition has failed — even when it briefly succeeded. A failed sensor produces the same lockout as a genuine ignition fault.
- Blocked or dirty burner Sometimes
A burner that has accumulated dust, debris, or corrosion products over time may not allow the gas-air mixture to flow correctly, making it difficult or impossible to establish a stable flame. This becomes more likely if the boiler has not been serviced for a number of years.
- Burner fan fault or wiring issue Sometimes
The fan is responsible for clearing combustion gases and drawing in fresh air before ignition. If the fan is running too slowly, intermittently, or not at all, the boiler's control board may refuse to proceed with the ignition sequence, or an established flame may not sustain itself. Worn fan bearings and loose wiring connectors are typical culprits.
- Gas valve failure Sometimes
The gas valve controls the flow of gas to the burner. A valve that sticks, fails to open on demand, or develops an internal fault will prevent any gas from reaching the burner regardless of how well the rest of the ignition system is functioning.
- PCB (printed circuit board) fault Rare
The control board orchestrates the entire ignition sequence. A damaged or failing PCB may send incorrect signals to the ignition components or fail to interpret sensor readings correctly, resulting in repeated lockouts even when the physical components are in reasonable condition. This is usually a diagnosis of exclusion reached after other components have been checked.
How to fix it
- Check that the gas supply to your home is working DIY safe
Before assuming the boiler is at fault, try another gas appliance such as a gas hob or gas fire. If those are also not working, the issue is likely with your supply rather than the boiler itself. Contact your gas supplier or National Gas (0800 111 999) if you suspect a supply outage. If you have a prepayment meter, ensure it has sufficient credit.
- Verify that the gas isolation valve on the boiler's gas supply pipe is fully open DIY safe
Locate the manual isolation valve on the gas pipe leading into the boiler — typically a quarter-turn valve. The handle should be in line with the pipe to indicate it is open. If it has been knocked to the closed position (handle across the pipe), turn it to open. Do not touch any other valves or internal gas components.
- Attempt a single reset of the boiler DIY safe
On most Alpha models, rotate the front selector dial to the RESET position and hold it there for approximately 30 seconds, then return it to its normal operating position. The boiler should attempt to re-ignite. If it fires up and runs normally, monitor it over the next 24 hours. If the 0A8 code returns straight away or after a short time, do not keep resetting — repeated failed resets will not fix the underlying fault and may cause further wear.
- If the fault persists after one or two resets, contact a Gas Safe registered engineer Gas Safe engineer
A qualified engineer will need to remove the boiler casing and carry out a systematic inspection of the ignition electrodes, ionisation probe, burner, fan, gas valve, and PCB wiring. Attempting to open the boiler casing or handle any of these components yourself is both dangerous and illegal without Gas Safe registration. Search the Gas Safe Register at gassaferegister.co.uk to find a qualified engineer in your area.
Parts you may need
- Ignition electrode assembly · from £35
- Ignition lead / HT lead · from £25
- Ionisation / flame sensing probe · from £30
- Burner fan (flue fan) · from £120
- Gas valve · from £150
- PCB (control board) · 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 £120–£380, depending on the underlying cause.
Frequently asked questions
Can I keep resetting my Alpha boiler to clear the 0A8 code?
You can try one or two resets to rule out a one-off nuisance trip, but repeatedly resetting a boiler that keeps locking out on 0A8 is not a fix and could cause additional wear to the ignition components. If the code returns after a reset or two, the boiler needs a proper inspection by a Gas Safe registered engineer.
How much does it typically cost to fix an Alpha 0A8 fault in the UK?
Most homeowners pay somewhere between £120 and £380 depending on which component is at fault. Ignition electrode or flame sensor replacements tend to sit at the lower end of that range (around £120–£180 including labour), while a fan or gas valve replacement typically costs £200–£350. PCB replacement is less common but can push costs higher — sometimes £350–£450 or more — which is worth weighing up against the age of the boiler. As a rough rule of thumb, if the repair bill exceeds half the cost of a replacement boiler and the boiler is over ten years old, a new installation may be more economical.
What is the difference between Alpha fault codes 0A8, 0A1, and E1?
All three codes fall within Alpha's ignition-failure category and indicate that the boiler has failed to establish or maintain a burner flame. The precise code displayed can vary by model and firmware version, but the diagnosis and repair process is essentially the same for all three: the engineer will work through the ignition electrode, flame sensor, gas supply, burner, fan, and gas valve in turn. If your display shows any of these codes, treat them as an ignition lockout and follow the same troubleshooting steps.
Will an annual boiler service help prevent the 0A8 fault from recurring?
Yes, significantly. During a service a Gas Safe engineer will clean or replace the ignition electrodes and flame sensor, inspect the burner and fan, and check gas pressure — all of which are the most common triggers for an 0A8 lockout. A service typically costs £70–£110 and is the single most effective way to catch deteriorating components before they cause an unexpected breakdown in winter.