Vokera 03 Fault Code: Causes, Fixes & Repair Costs
What does the Vokera 03 fault code mean?
The 03 code (displayed as A03 on some Vokera models) tells you the boiler has detected a problem with the flue fan — the component responsible for drawing fresh combustion air in and pushing waste gases safely out through the flue. When the boiler's control board doesn't receive the expected speed signal from the fan, or detects the fan isn't running correctly, it triggers a safety lockout to prevent unvented flue gases from accumulating. On older Vokera Linea models with a metal pump-proving switch, the same code can occasionally appear even though the fan itself is fine — the switch is the real culprit. Because a faulty fan is a potential safety risk, the boiler will not restart until the underlying fault is resolved.
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
- Worn or failed fan motor Common
The fan motor is the most common trigger for this code. Over time — especially on older Vokera Compact and Linea models whose fans have a reputation for premature wear — the motor windings or bearings deteriorate, causing the fan to spin too slowly, intermittently, or not at all. The boiler's PCB detects the incorrect speed signal and locks out.
- Blocked flue or air inlet Common
A partial or full blockage in the flue terminal or air intake pipe prevents the fan from achieving the airflow the boiler expects. Common causes include bird nests, debris, or a crushed or kinked flue pipe. The fan may still be spinning but the restricted airflow trips the fault.
- Loose or damaged fan wiring Sometimes
Vibration over years of operation can loosen the electrical connections at the fan's plug or along the wiring loom. Corrosion from a nearby micro-leak can also damage connector pins, causing an intermittent or absent speed signal to the PCB.
- Air pressure switch failure Sometimes
The air pressure switch monitors that the fan is producing adequate pressure differential before the burner fires. If the switch membrane perishes, the switch sticks, or its sensing tube becomes blocked with condensate, it can misreport fan status and trigger the 03 code even when the fan itself is working fine.
- Pump proving switch (older Linea models) Sometimes
Certain early Vokera Linea boilers were fitted with a metal pump proving switch that can generate a spurious 03 code unrelated to the fan or flue. If a Gas Safe engineer finds the fan and pressure switch are both healthy, this switch should be checked on those older models.
- PCB (control board) fault Rare
The PCB sends power to the fan and monitors the returning tachometer signal. A failed driver circuit or damaged signal input on the board can cause it to misread or not read fan speed at all, producing the 03 code even when the fan is mechanically sound. PCB faults are less common and should only be diagnosed after all other components have been ruled out with a multimeter.
How to fix it
- Check that nothing is blocking the flue terminal outside DIY safe
Go outside and visually inspect the flue outlet and, where accessible, the air intake terminal. Look for bird nests, leaves, debris, or anything physically blocking the opening. Do not reach into the flue — simply clear any obvious external obstruction and make sure the terminal guard (if fitted) is intact. If the flue is high up or on a roof, do not attempt to access it yourself.
- Listen to the boiler when it tries to start DIY safe
Stand near the boiler and initiate a heat demand (turn up the thermostat). You should hear the fan spin up before the burner fires. If you hear nothing at all, the fan may not be receiving power. If you hear a grinding, rattling, or intermittent whirring, the fan motor or its bearings are likely failing. Note what you hear and pass this information to your engineer — it helps narrow the diagnosis.
- Reset the boiler (up to twice) DIY safe
Press and hold the reset button (marked R on most models) for 3–5 seconds until the fault code stops flashing, then release. On selector-dial models, turn the dial to the reset or OFF/RESET position and hold for a few seconds. Allow the boiler a full start-up cycle before judging whether the code has cleared. Repeat once more if the first attempt fails. Do not reset more than two or three times in quick succession — repeated resets without fixing the root cause can damage the ignition components.
- Call a Gas Safe registered engineer to inspect and repair the fan and associated components Gas Safe engineer
If the fault code returns after resetting, a qualified engineer needs to attend. They will test the fan motor, wiring, and tachometer signal with a multimeter; inspect the air pressure switch and its sensing tube; check the flue for internal restrictions; and — only if all other components test correctly — assess the PCB. On older Linea models, they should also check the pump proving switch. The most common outcome is fan replacement, which is generally more cost-effective as a complete unit swap rather than a partial repair.
Parts you may need
- Flue fan assembly (Vokera compatible) · from £95
- Air pressure switch · from £35
- Fan wiring harness / connector · from £18
- PCB (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 £180–£350, depending on the underlying cause.
Frequently asked questions
Is the Vokera 03 fault code dangerous?
It can be, which is exactly why the boiler locks itself out when it detects the problem. If the fan isn't working properly, combustion gases including carbon monoxide may not be safely vented. Do not attempt to override the lockout or repeatedly reset the boiler hoping it will clear on its own — get a Gas Safe engineer to diagnose the cause before using the boiler again.
My Vokera keeps showing the 03 code but then clears itself — should I be worried?
An intermittent 03 code that resets itself is a warning sign, not reassurance. It typically points to a fan that is on its way out, a marginal wiring connection, or a partly blocked flue — any of which can worsen without notice. Book an engineer check sooner rather than later; intermittent faults are often cheaper to fix than a full breakdown later.
How much does it cost to fix a Vokera 03 fault code in the UK?
For most homeowners, the repair involves replacing the fan, which typically costs £200–£300 including parts and labour. An air pressure switch replacement is usually around £150–£200 all in. If the PCB turns out to be the fault, costs rise significantly — often £400–£600 — but a competent engineer should only reach that conclusion after testing all other components first with a multimeter. Always insist the engineer diagnoses the specific failed part before authorising a PCB replacement.
Is it worth repairing a Vokera boiler showing the 03 code, or should I replace it?
If the boiler is under seven years old and the fan is the only worn component, repair is usually the right call. If your Vokera is older and the engineer finds two or more parts showing significant wear — for example, the fan and the pump or heat exchanger — the combined repair bill can approach half the cost of a new boiler. In that scenario, investing in a new boiler with a manufacturer warranty is often the smarter long-term choice.