Alpha E75 Fault Code: Causes, Fixes & Repair Costs
What does the Alpha E75 fault code mean?
The E75 fault code on Alpha boilers — most commonly seen on the E-Tec and E-Tec Plus ranges — indicates that the PCB has detected a problem with the flue fan. This could mean the fan has failed to start, is running below the required speed, or is sending back incorrect speed-feedback signals to the control board. Because the fan is responsible for pushing combustion gases safely out through the flue, the boiler locks out immediately when this fault appears. It will not attempt to fire until the underlying problem is resolved, which is the correct safety response — without a working fan, harmful flue gases could accumulate inside the property.
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
- Worn or seized fan motor Common
The fan motor is in near-constant use whenever the boiler fires, and over time the bearings wear or seize, particularly in boilers installed in dusty loft spaces or plant rooms. A seized motor either fails to reach the required RPM or stops altogether, triggering E75.
- Loose or corroded wiring to the fan Common
Vibration from normal boiler operation can gradually loosen the electrical connections between the fan and the PCB. Corroded terminals — more likely in damp utility rooms or external enclosures — can also interrupt the speed-feedback signal, causing the PCB to report a fan fault even when the motor itself is intact.
- Flue blockage causing back-pressure Sometimes
A partially or fully blocked flue terminal — caused by a bird nest, debris, or ice in winter — creates abnormal back-pressure that prevents the fan from reaching its target speed. The boiler interprets this as a fan fault and locks out.
- Faulty PCB misreading fan signals Sometimes
If the PCB itself has aged, suffered moisture ingress, or developed a component fault, it may incorrectly interpret the fan's speed signal as out of range even when the fan is physically running correctly. This is less common but worth considering when the fan tests fine.
- Burnt-out motor windings Rare
A more severe form of motor failure where the internal windings have overheated and failed. Unlike bearing wear, this is not recoverable — the fan assembly must be replaced entirely.
How to fix it
- Check the gas supply to the property DIY safe
Make sure other gas appliances such as a hob or gas fire are working normally. If no gas appliances are working, the issue may be with your gas supply rather than the boiler. Contact your gas supplier before doing anything else.
- Inspect the flue terminal outside for obvious blockages DIY safe
Go outside and look at where the flue exits the building (usually a white plastic terminal on an external wall or roof). Check for visible obstructions such as bird nests, leaves, or ice build-up. Do not attempt to insert anything into the flue. If you can safely clear an external obstruction without tools or ladders, do so — otherwise note it for the engineer.
- Reset the boiler once DIY safe
Alpha E-Tec and E-Tec Plus boilers have a reset button on the control panel. Switch the boiler off and wait five minutes to allow any components to settle. Then press and hold the reset button for approximately five seconds until the display responds. Allow the boiler a full two minutes to attempt a restart. If E75 returns immediately or after a single firing attempt, do not reset again — repeated resets can mask a developing fault and in rare cases cause additional wear.
- Engineer inspection: check fan wiring and connections Gas Safe engineer
A Gas Safe engineer will isolate the boiler electrically and visually inspect all wiring connections at the fan motor and at the PCB. Loose or corroded terminals are re-secured or replaced with properly rated connectors, and the boiler is tested to confirm the speed-feedback signal is reaching the board correctly.
- Engineer test: measure fan speed and clean or replace the fan assembly Gas Safe engineer
Using the boiler's diagnostic or commissioning mode, the engineer will measure actual fan RPM against the manufacturer's specification. Fan blades will be cleaned if debris is contributing to reduced speed. If the motor is seized, the bearings are worn, or the windings have failed, the entire fan assembly will be replaced with a model-specific Alpha unit and airflow recalibrated.
- Engineer inspection: assess and replace PCB if required Gas Safe engineer
If the fan tests within specification but E75 persists, the PCB is the likely cause. The engineer will check for moisture ingress or visible component damage. A dry-out may resolve a minor moisture issue, but a board with failed components will need to be replaced. PCB replacement on Alpha boilers is model-specific and must be programmed correctly after fitting.
- Call a Gas Safe registered engineer Gas Safe engineer
If the boiler has not been restored to normal operation after the checks above, arrange a visit from a Gas Safe registered engineer. You can verify any engineer's registration at gassaferegister.co.uk. Do not attempt to open the boiler casing or handle any internal components yourself — this is a legal requirement under Gas Safety (Installation and Use) Regulations 1998.
Parts you may need
- Alpha E-Tec fan assembly · from £110
- Fan wiring loom / connector kit · from £18
- Alpha E-Tec PCB · from £195
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–£380, depending on the underlying cause.
Frequently asked questions
Is the Alpha E75 fault dangerous?
Yes, you are right to take it seriously. The fan is what pushes combustion gases — including carbon monoxide — safely out through the flue. The boiler correctly locks out when E75 appears to prevent harmful gases from building up inside your home. Do not attempt to bypass the lockout or repeatedly reset the boiler. Ensure you have a working carbon monoxide alarm fitted near the boiler while the fault remains unresolved.
Can I fix the E75 fault myself?
Very limited checks are safe for a homeowner: verifying your gas supply is on, looking for an obvious blockage at the external flue terminal, and attempting a single boiler reset. Everything beyond that — opening the casing, handling the fan, testing wiring, or touching the PCB — must be carried out by a Gas Safe registered engineer. Attempting internal boiler work yourself is illegal under UK gas safety regulations and will void any remaining warranty.
How much does it typically cost to fix Alpha E75?
For the most common repair — fan assembly replacement including parts and labour — expect to pay in the region of £150 to £380. A straightforward wiring fix or flue clearance will sit at the lower end. If the PCB turns out to be the root cause, replacement parts alone can cost £180–£250 or more, pushing the total bill higher. If your boiler is over ten years old and facing a PCB or fan replacement, it is worth getting a new boiler quote at the same time, as the economics can favour replacement over repair.
Will an annual service prevent the E75 fault from coming back?
A yearly service by a Gas Safe engineer is the single most effective way to reduce the risk of fan-related faults. During a service the engineer will check fan operation, clean blades, inspect wiring connections, and spot early signs of bearing wear before they cause a full lockout. Boilers that are serviced annually consistently have fewer breakdowns than those that are not.