F.162 Burner in a fault state Processor low voltage Turn the appliance off and on again
The F162 error code on Viessmann boilers indicates f.162 burner in a fault state processor low voltage turn the appliance off and on again.
Viessmann F162 means: f.162 burner in a fault state processor low voltage turn the appliance off and on again. The usual causes are boiler has entered safety lockout due to a previous fault, safety device has tripped (overheat thermostat, flame failure) or transient fault that has cleared. You can safely reset the boiler once — if F162 returns, do not keep resetting. A qualified heating engineer should diagnose the root cause.
What Does F162 Mean
The F162 code is shown by the boiler’s control board when it detects f.162 burner in a fault state processor low voltage turn the appliance off and on again. The boiler then stops instead of continuing to run in that condition: the code is the appliance reporting a problem, not proof that the boiler is broken.
| What you see on the boiler |
|---|
| The display shows F162 and the boiler stops until the fault is cleared |
Common Causes
Causes documented in 2 technical sources.
| Cause |
|---|
| Boiler has entered safety lockout due to a previous fault |
| safety device has tripped (overheat thermostat, flame failure) |
| transient fault that has cleared |
Safety Warning
F162 involves electrical or pressure-related components. Do not attempt repairs without proper qualifications. Ensure the boiler is electrically isolated before any inspection. If you notice water leaks, unusual sounds, or pressure anomalies, contact a qualified heating engineer immediately.
Parts & Prices
Prices shown are indicative. Actual prices and availability vary by region.
Step-by-Step Diagnosis
1. Note the original fault code that caused the lockout. 2. Investigate and resolve the underlying cause before resetting. 3. Check the fault history in the boiler's diagnostic menu. 4. Do not repeatedly reset without investigation — repeated lockouts indicate a persistent problem
How to Fix It
Resolve the underlying fault first
reset the boiler by pressing the reset button (typically hold for 3-5 seconds)
if the boiler locks out again within a short period, do not continue resetting — call a qualified engineer
Refer to the Viessmann service documentation for the detailed procedure. Only a qualified engineer should carry out these repairs.
Diagnostic Tools
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Affected Models
Viessmann models that can display fault code F162:
| Model Family | Output Range | Frequency |
|---|---|---|
| All Viessmann models | — | Possible |
Frequently Asked Questions
Resolve the underlying fault first. According to the technical documentation, this is the first check on the list for F162.
F162 is not classified as a high-severity fault, so the boiler can be reset once. If F162 comes back, stop resetting: the underlying cause is still there and needs a qualified heating engineer.