Viessmann FE Fault Code: Causes, Fixes & Repair Costs
What does the Viessmann FE fault code mean?
The FE code on a Viessmann boiler indicates a fault linked to the printed circuit board (PCB) or a problem with the fan failing to reach a standstill position when expected. In practical terms, the boiler's control electronics have detected something they cannot recover from automatically — either the PCB itself has developed a fault, the fan is still spinning when it shouldn't be, or an electrical plug-in connection associated with the fan circuit is unreliable. Because the PCB governs virtually every other component in the boiler, this fault causes the appliance to lock out as a precaution. Note that the exact diagnosis can vary between Viessmann models, so a Viessmann-trained Gas Safe engineer is best placed to confirm the root cause on your specific appliance.
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 damaged PCB Common
The PCB is the boiler's central control unit, managing everything from ignition to temperature regulation. Solder joints on the board can deteriorate, burn out, or work loose over time — especially in boilers exposed to repeated heat cycling. When these connections fail, the board can no longer operate reliably and the FE code is triggered. In some cases only a small section of the board is affected; in others the damage is extensive enough to warrant full replacement.
- Fan not reaching standstill Sometimes
Viessmann boilers monitor the fan's status throughout the operating cycle. If the fan continues to spin when the boiler expects it to have stopped — for instance, due to a failing fan motor or a faulty fan speed sensor — the control board detects the discrepancy and locks the boiler out with the FE code. This is a protective measure to prevent the burner from firing under unsafe airflow conditions.
- Loose or unstable wiring and plug-in connections Sometimes
The wiring harness connecting the fan to the PCB, or the plug-in connectors at either end, can loosen due to vibration or age. An intermittent connection can cause the PCB to receive incorrect signals, mimicking a board fault even when the board itself is in reasonable condition. An engineer can sometimes identify and reseat or replace the affected connector relatively quickly.
- Fan motor failure Rare
If the fan motor itself has seized or is drawing abnormal current, the PCB will detect the irregular behaviour and flag it. A failed fan motor will need replacement before the boiler can return to normal operation.
How to fix it
- Check whether other gas appliances in the property are working DIY safe
Before assuming the boiler is at fault, confirm that your gas hob or gas fire (if you have one) is functioning normally. If no gas appliances are working, the issue may be with your gas supply — contact your gas supplier rather than a boiler engineer.
- Note any additional error information on the display DIY safe
Some Viessmann models display supplementary codes or flashing sequences alongside FE. Take a photo of the display and note down anything you see — this information will help the engineer diagnose the fault more quickly when they arrive.
- Do not repeatedly reset the boiler DIY safe
With the FE fault code, resetting the boiler is generally not recommended as a first response. At most, a single reset attempt is reasonable to see if the fault clears — but if it returns immediately, stop. Repeated resets with a PCB or fan fault can expose internal components to further stress and potentially increase repair costs. Do not attempt more than one reset.
- Arrange for a Gas Safe registered engineer to inspect the boiler Gas Safe engineer
The FE fault requires a qualified engineer to open the boiler casing, inspect the PCB, check the fan motor and its wiring, and test the plug-in connections. This is not a task a homeowner should attempt. The engineer will use diagnostic equipment to determine whether the fault lies with the wiring, the fan, a repairable section of the PCB, or the board as a whole.
- Engineer to inspect and test the fan and its electrical connections Gas Safe engineer
The engineer will check that the fan spins freely, verify its speed sensor is reading correctly, and inspect the wiring loom and connectors between the fan and the PCB for signs of looseness, corrosion, or damage. Reseating a connector or replacing a short section of wiring is the least expensive possible outcome.
- Engineer to inspect, repair, or replace the PCB Gas Safe engineer
If the fan and wiring are found to be in good order, or if solder joints on the PCB are visibly damaged, the engineer will assess whether the board can be repaired (e.g. resoldering joints, replacing individual components) or whether a full PCB replacement is the only viable option. They will advise on cost before proceeding.
Parts you may need
- Viessmann PCB (boiler-specific) · from £280
- Fan motor assembly · from £120
- Fan speed sensor / hall sensor · from £35
- Wiring harness / plug-in connector set · from £25
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–£500, depending on the underlying cause.
Frequently asked questions
Can I fix a Viessmann FE fault code myself?
No. The FE code points to a fault inside the boiler's electronics — either the PCB, the fan circuit, or the wiring connecting them. Accessing these components requires opening the boiler casing and working with mains electrical and gas-connected parts. This must only be done by a Gas Safe registered engineer. Attempting it yourself could be dangerous and would likely invalidate your boiler warranty.
How much does it cost to fix a Viessmann FE fault?
It depends on what the engineer finds. If the problem turns out to be a loose wiring connector or a straightforward solder repair, you might pay £150–£200 including the call-out and labour. A fan motor replacement typically adds £100–£180 in parts on top of labour. A full PCB replacement — which is the most common significant repair for this code — usually comes to around £400–£500 all in. If your boiler is over 10–12 years old and the PCB has failed, your engineer may suggest that a new boiler is more cost-effective in the long run, as new Viessmann models can cost from around £2,100 installed.
Why does the FE code mention the fan if it's a PCB fault?
The two are closely linked. The PCB continuously monitors the fan's status — checking that it's running when it should be and stopped when it shouldn't. If the fan fails to reach standstill, or if the electrical connection between the fan and the PCB is unreliable, the PCB registers a fault and displays FE. So the fault code can originate with either component. An engineer will test both before deciding on the repair.
My Viessmann boiler keeps showing FE after being reset — is that normal?
It's a sign that the underlying fault has not been resolved. Resetting clears the lockout temporarily, but if the PCB or fan circuit has a genuine fault, the code will return — sometimes within seconds. Repeated resets are not recommended for this particular code as they can put additional strain on already-compromised components. If the fault keeps coming back, stop resetting and call a Gas Safe engineer to carry out a proper diagnosis.