Alpha E38 Fault Code: Causes, Fixes & Repair Costs
What does the Alpha E38 fault code mean?
The E38 code indicates that your Alpha boiler has repeatedly lost its flame signal while running. In practical terms, the boiler successfully ignites, but something is then causing it to lose confirmation that the flame is still burning — so it shuts down automatically as a safety precaution. A small ionisation electrode sits in the burner and detects the live flame by measuring a tiny electrical current. The moment that current disappears, the boiler cuts the gas supply to prevent any risk of a leak. When this happens again and again, E38 is logged. Important note on how E38 appears on your display: on many Alpha InTec and InTec² models, the live fault code shown on the display is actually E43 (loss of flame rectification), while E38 is the underlying code stored in the boiler's INFO fault history menu — it is the explanation for why E43 keeps occurring. If your engineer reads out E38 from the fault history, or your display shows E43 on a repeated basis, this page covers both situations. Models that log E38 include the Alpha InTec, InTec², InTec GS, InTec S, and E-Tec ranges.
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.
Common causes
- Dirty or faulty flame sensing electrode or lead Common
The ionisation electrode is the most common culprit for this fault. Over time, carbon deposits build up on the electrode tip, insulating it and preventing it from reading the flame correctly. The lead connecting the electrode to the PCB can also crack or corrode, giving an intermittent signal. This is normally the first thing a Gas Safe engineer will inspect and is often resolved by cleaning or a straightforward replacement.
- Low gas supply pressure or interrupted gas supply Common
If the working gas pressure arriving at the burner is too low, the flame will be weak and unstable, causing repeated signal loss. This can happen because the main meter cock is partially closed, there is an issue with the mains supply in your area, or a gas pressure regulator is beginning to fail. Checking whether other gas appliances in the home are working normally is a quick first indicator.
- Flue gas recirculation or wind-induced combustion disruption Sometimes
If combustion exhaust gases are being drawn back into the air intake — particularly when the flue terminal is exposed to strong or gusty winds — the air-to-gas mixture in the burner is disrupted. Alpha's own service guidance specifically flags high wind conditions as a trigger for E38. The flue terminal position, any nearby obstructions, and the condition of the flue itself all need to be checked by an engineer.
- Gas valve settings out of tolerance Sometimes
The gas valve controls exactly how much gas reaches the burner. If its minimum or maximum rate settings have drifted out of the correct range, the burner flame can become unstable or drop out during modulation. An engineer can test the valve output and recalibrate or replace it if required.
- Incorrect fan speed or fan wiring fault Sometimes
The fan draws combustion air through the burner at a precise rate. If the fan is running too slowly, too fast, or intermittently due to a wiring fault or a failing fan motor, the air-to-gas ratio shifts and the flame becomes unreliable. Alpha's service checklist for E38 specifically includes verifying fan speed and checking all wiring connections to the fan.
- PCB fault Rare
If the PCB — the boiler's main control board — is giving false readings or failing to correctly process the signal from the flame sensing electrode, E38 can be logged even when the electrode itself is clean and the gas supply is fine. PCB faults are usually only confirmed after all other causes have been ruled out, as they are the more expensive repair.
How to fix it
- Check that your gas supply is working DIY safe
See whether other gas appliances in your home — a gas hob or gas fire, for example — are lighting and working normally. If they are not, the issue is likely with the gas supply to your property rather than the boiler itself. Contact your gas supplier or call the National Gas Emergency Service on 0800 111 999 if you suspect a supply problem or smell gas.
- Inspect the flue terminal from outside DIY safe
Go outside and look at the point where the flue exits the building. Check that it is not physically blocked by debris, a bird nest, frost, or any object that could restrict airflow. Do not attempt to dismantle or reach inside the flue — this is an external visual check only. If the flue terminal is clearly blocked and you cannot safely clear it from outside at ground level, leave it for an engineer.
- Attempt a single boiler reset DIY safe
If the gas supply is confirmed to be on and there is no obvious flue blockage, you can try resetting the boiler once. On most Alpha models this involves pressing and holding the reset button on the control panel for approximately five seconds. Wait for the display to return to its normal operating state. If E38 or E43 reappears promptly after reset, do not reset again — repeated resets without fixing the root cause can mask a more serious problem. Move on to calling an engineer.
- Have a Gas Safe engineer inspect and clean or replace the flame sensing electrode and lead Gas Safe engineer
This is the most common fix for E38. The engineer will access the combustion chamber, remove the electrode, clean off any carbon deposits (or replace the electrode entirely if it is worn or cracked), and check the condition of the connecting lead. This is internal gas appliance work and must only be performed by a Gas Safe registered engineer.
- Have the engineer test gas valve operation and adjust settings if necessary Gas Safe engineer
The engineer will measure the working gas pressure at the burner and verify that the gas valve is delivering the correct rate at both minimum and maximum. If the valve is out of tolerance it may be recalibrated; if it has failed it will need to be replaced. This is a gas component and is not DIY-safe under any circumstances.
- Have the engineer check fan operation and wiring Gas Safe engineer
The engineer will verify the fan is running at the correct speed for the boiler's output, check that all wiring connections to the fan are secure and free from corrosion, and confirm the fan is not intermittently cutting out. A faulty fan motor or loose connection can be replaced or rectified at this stage.
- Have the engineer assess for flue gas recirculation Gas Safe engineer
If the above checks do not identify a clear cause, the engineer will assess whether exhaust gases are being recirculated back into the air intake. This may involve inspecting the flue terminal position, checking for any structural changes near the flue exit, or verifying the flue system integrity. Remediation could involve repositioning the flue terminal or fitting a wind deflector.
- If all else fails, have the PCB tested and replaced if necessary Gas Safe engineer
A PCB replacement is the last resort once all other components have been checked and found to be in good order. The engineer will test the board's outputs and, if it is confirmed faulty, replace it with a compatible unit. This is the most expensive repair for this fault code — see the FAQ for more detail on costs.
Parts you may need
- Flame sensing (ionisation) electrode · from £18
- Electrode connecting lead · from £15
- Gas valve (Alpha InTec / E-Tec compatible) · from £120
- Fan / air pressure assembly · from £95
- PCB (main control board) · from £180
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 £100–£350, depending on the underlying cause.
Frequently asked questions
My boiler shows E43, not E38 — why does this page mention both?
On Alpha InTec and InTec² boilers, E43 is the live fault code displayed on screen when the boiler locks out due to repeated flame signal loss. E38 is the code stored in the boiler's internal INFO fault history menu, which records the underlying reason E43 has been triggered. They describe the same root problem — the boiler is repeatedly losing its flame signal during operation. When a Gas Safe engineer reads the fault history, they will typically see E38. Both codes are covered here because users searching for either are dealing with the same fault.
Can I fix Alpha E38 myself?
There are a few safe checks a homeowner can do: confirming the gas supply is on, doing a quick external visual check of the flue terminal for obvious blockages, and attempting one reset. Beyond that, all diagnostic and repair work must be carried out by a Gas Safe registered engineer. It is illegal for an unregistered person to work on gas appliances in the UK, and opening the boiler casing to access the electrode, gas valve, fan, or PCB falls into that category. You can verify your engineer's registration at gassaferegister.co.uk.
How much does it typically cost to fix Alpha E38 in the UK?
For the most common cause — a dirty or failed flame sensing electrode and lead — expect to pay roughly £100–£180 all-in, including callout, labour, parts, and VAT. If the gas valve needs adjustment the engineer's time may add a little more, but recalibration alone rarely pushes beyond £200. If the valve needs replacing, or the fan motor has failed, total costs typically fall in the £200–£350 range, which is where most people with this fault end up. A PCB replacement is significantly more expensive — usually £350–£550 or above depending on the model and parts availability — but this is only needed in a minority of cases. If your boiler is over ten years old and facing a repair costing £400 or more, it is worth getting a new boiler quote at the same time.
Why does E38 keep coming back after a reset?
Resetting the boiler clears the lockout so it can attempt to fire again, but it does not fix the underlying fault. If E38 or E43 returns within a short time after reset, the root cause — most likely a degraded flame sensing electrode, a gas pressure issue, or a flue problem — is still present. Repeatedly resetting without investigation is not recommended and can, in some cases, indicate a combustion problem that warrants prompt attention. Book a Gas Safe engineer rather than cycling through multiple resets.