Alpha 0E99 Fault Code: Causes, Fixes & Repair Costs
What does the Alpha 0E99 fault code mean?
The code '0E99' is not listed in Alpha's standard published fault code tables for any of its current or recent model ranges (E-Tec, E-Tec Plus, Evoke, Protec Plus, Intec, or CD series). If your display is showing this, the most likely explanation is a misread of the digits — common culprits are E09 (ignition failure), E90 (pressure switch or overheating safety fault), or E99 (a general internal/electronic lockout used on some models). On older Alpha digital displays the screen can show a leading zero before certain codes, making 'E99' appear as '0E99'. Until you can confirm the exact code from your boiler's manual, treat this as a potential PCB or internal electronic fault and follow the steps below. Related codes worth knowing: E83 (PCB communication error between internal boards), E84 (external sensor or outdoor probe connection failure causing incorrect temperature readings), E85 (internal PCB circuit failure or firmware fault), and E90 (pressure switch or overheat safety device malfunction).
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
- Display misread — code is actually E09, E90, or E99 Common
Alpha boiler screens can be difficult to read clearly, especially on older units. A leading zero can appear before certain fault codes, turning 'E99' into what looks like '0E99'. E09 relates to ignition failure, E90 to a pressure switch or overheat safety fault, and E99 to a general internal lockout. Checking the boiler's manual for your specific model is the single most useful first step.
- PCB communication or internal circuit fault (E83 / E85) Common
The printed circuit board is the electronic brain of the boiler, coordinating every component. A general communication breakdown between the PCB and other internal boards (E83) or an internal circuit failure within the PCB itself (E85) can cause the boiler to lock out and display an unusual or unrecognised code. Age, damp, and general component wear are the most frequent underlying reasons.
- Water ingress or internal leak onto the PCB Sometimes
A slow leak from a nearby component — such as the heat exchanger, pump seals, or pipework joints — can allow water to drip onto the PCB over time. Even small amounts of moisture can cause short circuits, corrosion on the board, and intermittent or permanent lockouts.
- Electrical power surge Sometimes
A sudden spike in the mains supply — from a nearby lightning strike, a grid fluctuation, or a faulty consumer unit — can damage delicate PCB components, the ignition module, or sensor circuits simultaneously. Boilers without surge protection are particularly vulnerable.
- Loose or damaged wiring to sensors or the PCB Sometimes
Vibration over years of operation, or previous repair work, can leave wiring connectors partially seated. The PCB may then receive erratic signals from sensors (such as the external outdoor probe flagged by E84) and respond with an unrecognised or catch-all fault code.
- Faulty external sensor or probe (E84) Rare
If an outdoor temperature sensor or a secondary thermistor has failed or become disconnected, the boiler cannot calculate heat demand correctly. The PCB logs this as a sensor communication fault (E84 on some Alpha models) and may lock out as a precaution.
How to fix it
- Cross-check the exact code shown on the display against your boiler manual DIY safe
Before doing anything else, look up the fault code table for your specific Alpha model. The manual will be named after your boiler (e.g. Alpha E-Tec 28 Installation & Servicing Manual) and is freely available on the Alpha Boilers website. Confirm whether the code is 0E99, E99, E90, E09, or something else entirely — this one step can save unnecessary call-out costs.
- Check your gas supply is working DIY safe
Turn on a gas hob or check that your gas meter's emergency control valve is fully open (handle in line with the pipe). If other gas appliances are also not working, contact your gas supplier rather than an engineer, as the fault lies outside the boiler.
- Check and restore boiler system pressure if needed DIY safe
Look at the pressure gauge on the front of the boiler. Normal operating pressure is typically 1–1.5 bar when the system is cold. If it reads below 0.8 bar, use the filling loop (the braided silver hose beneath the boiler) to top up slowly until the gauge reads around 1.2 bar, then close the filling loop valves firmly. A boiler that repeatedly loses pressure has an underlying fault and needs an engineer.
- Attempt a boiler reset (no more than 2–3 times) DIY safe
Locate the reset button — on most Alpha models it is a dedicated button or a turn-and-hold function on the control panel; your manual will show the exact method. Hold it for 3–5 seconds, release, and allow the boiler 2–3 minutes to attempt a full restart. If the code clears and the boiler fires normally, monitor it over the next 24 hours. If the fault returns, do not keep resetting — repeated unsuccessful resets can mask the underlying cause and may make diagnosis harder for an engineer.
- Call a Gas Safe registered engineer to diagnose the fault Gas Safe engineer
If the code persists after the checks above, the boiler needs professional diagnosis. An engineer will use specialist test equipment to read any stored fault history from the PCB, check all sensor readings and wiring connections, test the pressure switch and safety devices, and determine whether a component (such as a sensor, wiring loom, or the PCB itself) needs repair or replacement. Do not attempt to remove the boiler casing or touch any internal components — this is a legal requirement as well as a safety one.
- Contact Alpha directly if the boiler is still under warranty DIY safe
Alpha boilers typically carry a manufacturer's warranty of 7–10 years depending on the model and whether annual services have been carried out by a Gas Safe engineer. If your boiler is within this period and services are up to date, contact Alpha's customer support line before commissioning an independent engineer — a warranty repair will be at no cost to you.
Parts you may need
- Alpha boiler PCB (model-specific) · from £220
- Outdoor/external temperature sensor · from £35
- NTC thermistor (flow or return sensor) · from £25
- Pressure switch · from £45
- Wiring loom or connector harness · from £55
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 £150–£450, depending on the underlying cause.
Frequently asked questions
Why doesn't '0E99' appear in the Alpha fault code list?
Alpha's published fault code tables for all current and recent models — including the E-Tec, Evoke, and Protec Plus ranges — do not include a code called 0E99. The most likely explanation is a display misread: some Alpha screens show a leading zero before certain codes, so 'E99' can appear to read '0E99'. It is also worth checking whether the code is actually E09 (ignition fault) or E90 (pressure switch or overheat safety fault), as the digits on small digital displays can be easy to confuse. Always verify against the fault code table in your specific model's manual, available free on the Alpha Boilers website.
How much does it cost to fix a PCB fault on an Alpha boiler in the UK?
For most PCB-related repairs on an Alpha boiler, expect to pay in the region of £150–£450 including parts, labour, and VAT. A straightforward fix such as reseating a loose wiring connector or replacing a faulty sensor sits at the lower end. A full PCB replacement — which involves sourcing a model-specific board — typically costs £300–£450 when you include the engineer's time. In London and the South East prices tend to be 10–20% higher. Note that if the PCB on an older boiler has been damaged by a water leak or a power surge, the total bill can occasionally exceed £500, at which point it is worth getting a new boiler quote for comparison.
Can I reset my Alpha boiler myself to clear this fault?
Yes — a single reset attempt is a sensible first step and is safe to do yourself. Hold the reset button for 3–5 seconds (the exact method varies by model — check your manual), then give the boiler a few minutes to restart. If it fires up and runs normally, monitor it for 24 hours. However, if the fault code returns after one or two resets, stop resetting and call a Gas Safe engineer. Repeatedly resetting without addressing the underlying cause can mask important fault data and, in some cases, cause additional wear on components.
Is my Alpha boiler still under warranty, and does that cover this fault?
Alpha offers manufacturer warranties of 7–10 years on most current models, provided the boiler has been serviced annually by a Gas Safe registered engineer and the warranty was registered at installation. If your boiler is within this window and your service records are in order, contact Alpha's customer services before booking an independent engineer — a valid warranty claim means the repair should cost you nothing. If the warranty has lapsed, an independent Gas Safe engineer is your next step.