Viessmann Boiler Error Codes: Full UK Guide (2025)
A complete breakdown of Viessmann boiler fault codes — including F2, F4, F5, A3, A8, EE, 0C and more. Covers Vitodens 050-W, 100-W, 111-W and 200-W.
Viessmann Boiler Error Codes: Full UK Guide (2025)
Viessmann boilers such as the Vitodens 050-W, 100-W, 111-W, and 200-W are known for high efficiency and strong engineering — but they do experience repeated error codes, especially during winter months in the UK.
This guide covers all major Viessmann error codes, their causes, fixes, and typical UK repair prices.
Useful links:
Most Common Viessmann Error Codes
F2 – Ignition Failure
The most common Viessmann issue in the UK.
Causes:
- Faulty electrode
- Blocked burner
- Gas pressure issue
Typical UK Cost: £140–£320
F4 – Flame Detection Fault
Often appears when boilers haven't been serviced.
Causes:
- Dirty flame sensor
- Blocked heat exchanger
- Poor combustion
Cost: £120–£260
F5 – Fan Fault
Fan speed outside tolerance.
Cost: £180–£350
A3 – Pump Overrun Fault / Flow Issue
Meaning: Pump not circulating water properly.
Causes:
- Airlocked pump
- Sludge in system
- Weak circulation
Cost: £150–£320
A8 – Temperature Sensor Fault
Common on Vitodens 100-W.
Fix: Replace NTC sensor.
Cost: £80–£150
Additional Viessmann Fault Codes
EE – PCB Communication Fault
Affects older models.
Cost: £250–£480
0C – Low Pressure / Circulation Fault
Similar to A3.
Fix: Repressurise to 1–1.5 bar.
Cost: £0–£120
F9 – Gas Valve Error
Cost: £220–£420
E9 – Overheat Lockout
Often caused by sludge or poor circulation.
Cost: £150–£350
Frozen Condensate Issues (UK Winter)
Viessmann boilers frequently show F2, F4, and A3 when the condensate pipe freezes.
Fix:
- Pour warm water on pipe
- Reset boiler
- Fit pipe insulation
Cost: £0–£80
Viessmann Boiler Repair Costs (UK 2025)
| Fault | Cost |
|---|---|
| Ignition/fan issues (F2/F5) | £140–£350 |
| Flame issues (F4) | £120–£260 |
| Pump/flow issues (A3/0C) | £150–£320 |
| Sensor faults (A8) | £80–£150 |
| PCB/communication (EE) | £250–£480 |
| Annual service | £70–£90 |
Should You Repair or Replace?
You should consider replacement if:
- Boiler is 12+ years old
- EE or F5 errors repeat
- Repair cost is £500+
- Heat exchanger is blocked beyond flushing
Protection options:
Final UK Advice
Viessmann boilers are reliable but sensitive to pressure, ignition and burner cleanliness.
Keep your boiler running efficiently by:
- Booking an annual service
- Maintaining radiators & system pressure
- Insulating external pipes
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