Viessmann F31: Temperature Sensor Open Circuit
What the Viessmann F31 error code means, what causes it, and why it's a job for a licensed BC gas technician — not a DIY reset.
Severity
Moderate — book a service visit
What the Viessmann F31 error code means
A temperature sensor is reading an open circuit (disconnected or failed).
On Viessmann Vitodens 100-W, 200-W and 222-F series, F31 is a temperature-sensor fault. It is a protective response — the boiler is telling you something needs attention, and the safe, lasting fix is a proper diagnosis rather than repeated resets.
Symptoms you may notice
- Erratic heating or hot-water temperature
- Boiler locks out or refuses to fire
- Wrong temperature shown on the display
Common causes of Viessmann F31
Why this is not a DIY fix
A faulty NTC/thermistor reading (open, shorted or out-of-range) can mask a real overheating or circulation problem. A technician verifies whether the sensor itself has failed or whether it is correctly reporting a deeper fault before any part is replaced.
In British Columbia, gas work must be performed by a TSBC-licensed gas fitter. GasBoilers.ca — a CanroHeat division — sends Red Seal–certified, gas-licensed technicians who diagnose the true cause, repair it correctly, and verify safe operation before they leave.
How our technicians diagnose & repair it
- 1Measure sensor resistance against the manufacturer temperature curve
- 2Inspect wiring, connectors and sensor mounting/contact
- 3Confirm actual water temperature with calibrated instruments
- 4Replace the sensor and verify correct readings across the range
Related Viessmann codes
Viessmann F31 — FAQ
What does the Viessmann F31 error code mean?
A temperature sensor is reading an open circuit (disconnected or failed). On Viessmann Vitodens 100-W, 200-W and 222-F series, this is categorised as a temperature-sensor fault.
What causes Viessmann F31?
The most common causes are: Failed sensor; Broken wire; Loose connector. A licensed technician confirms which one applies before any part is replaced.
Can I fix Viessmann F31 myself?
No. A faulty NTC/thermistor reading (open, shorted or out-of-range) can mask a real overheating or circulation problem. A technician verifies whether the sensor itself has failed or whether it is correctly reporting a deeper fault before any part is replaced. Repeatedly resetting the boiler without fixing the root cause can be unsafe and can cause further damage. Call GasBoilers.ca at 604-359-1081 for a licensed diagnosis.
Is the Viessmann F31 error code dangerous?
This is a protective fault — the boiler has shut down a function to protect itself. It is best diagnosed promptly by a licensed technician so the underlying cause does not lead to a more expensive failure.
How much does it cost to fix Viessmann F31 in Greater Vancouver?
Cost depends on the root cause and any parts needed. We start with a flat-rate diagnostic, then quote the repair before any work begins — no surprises. Call 604-359-1081 for current pricing and same-day availability.
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