Common problems guide

The most common Viessmann Vitodens 111-W B1LA 35kW problems

The faults most likely to send a Viessmann Vitodens 111-W B1LA 35kW into lockout — with plain-English causes, what to check first, estimated repair costs and whether you need a Gas Safe engineer.

This model is discontinued. Parts can be harder to source and expensive. If repair costs are mounting, a new A-rated boiler may be the smarter choice.
25 documented codes
6 most common
0 DIY-safe checks
6 engineer needed

The 6 most common faults

01
30 High Engineer

Your boiler has stopped because it is getting an impossible temperature reading from one of its internal sensors, so it has shut down heating and hot water as a safety precaution.

Est. cost
£120-220
Parts
Boiler water temperature sensor (NTC), Sensor wiring harness or connector, Control PCB (only if the sensor and wiring are fine)
Full guide for 30
02
38 High Engineer

The boiler has lost the connection to one of its temperature sensors, so it can't read the water temperature properly and has likely stopped heating your home and hot water until it's looked at.

Est. cost
£120-220
Parts
Boiler water temperature sensor (flow sensor), Sensor wiring harness or connector, Main PCB (only if the fault persists after the sensor is replaced)
Full guide for 38
03
51 High Engineer

Your boiler has detected a problem with one of its internal temperature sensors, so it may stop heating your home or producing hot water until a qualified engineer replaces or repairs the faulty part.

Est. cost
£120-250
Parts
Outlet temperature sensor (flow sensor), Sensor wiring harness, Control PCB (only if the sensor and wiring are fine)
Full guide for 51
04
58 High Engineer

Your boiler has lost contact with the sensor that checks the temperature of your hot water cylinder, so it may not be heating your stored hot water properly, though your central heating may still work.

Est. cost
£120-250
Parts
Cylinder temperature sensor, Sensor cable or connector
Full guide for 58
05
59 High Engineer

The boiler has lost its reading of how hot the water leaving it is, so it has stopped as a precaution and will need a qualified engineer to check and replace a small sensor.

Est. cost
£120-220
Parts
Outlet (flow) temperature sensor, Sensor wiring harness or plug, Control PCB (only if the sensor and wiring test good)
Full guide for 59
06
b0 High Engineer

The boiler has lost track of how hot its exhaust gases are, so it has switched itself off as a precaution and will need a qualified engineer to check the sensor.

Est. cost
£120-220
Parts
Flue gas temperature sensor, Flue sensor wiring harness, Main control PCB (only if the fault is traced to the board)
Full guide for b0
Parts most often replaced

on the Viessmann Vitodens 111-W B1LA 35kW

Boiler water temperature sensor (NTC)Sensor wiring harness or connectorControl PCB (only if the sensor and wiring are fine)Boiler water temperature sensor (flow sensor)Main PCB (only if the fault persists after the sensor is replaced)Outlet temperature sensor (flow sensor)

Based on parts cited in our fault code database. Your engineer will confirm what's actually needed after diagnosis.

Call a Gas Safe engineer if…

  • You can smell gas or see signs of a leak
  • The Viessmann shows an Emergency or High severity code
  • The boiler keeps locking out after repeated resets
  • You've tried the DIY checks and the fault hasn't cleared
  • There's visible water leaking from the boiler
  • The flame is yellow or orange instead of blue
See the full 25-code list for the Viessmann Vitodens 111-W B1LA 35kW

Related guides

Boiler losing pressure → No hot water → When to replace → Symptom checker →