Viessmann fault code 402
Fault code 402 on a Viessmann boiler (including Vitodens 050-W) means: Central electronics module HBMU defective. Reset the appliance once. If the code comes back, a part is usually faulty. You can check the water pressure and settings yourself; leave work on gas-carrying parts to a certified gas engineer.
After a safety alert (gas, flue gas, combustion), reset no more than once and call in a certified gas engineer. If you smell gas, call your national gas emergency number or 112 immediately.
Cause
Fault code 402 on a Viessmann boiler indicates: Central electronics module HBMU defective.
Applies to
Viessmann Vitodens 050-W, -.
Matching parts
Viessmann parts are available from Instalpunt; shipping to EU countries from €17.95 (€24.95 for more distant countries), usually 3–5 working days.
This message does not point directly to one faulty part. If the code keeps coming back, view the Viessmann parts:
Fix it yourself or call an engineer?
Always consult the manual for your appliance and work safely. If in doubt or if the fault comes back, call in a qualified professional. A question about a part? Write to us at info@instalpunt.nl.
Frequently asked questions
What does Viessmann boiler fault code 402 mean?
Central electronics module HBMU defective.
How do I fix fault code 402 on a Viessmann boiler?
First check the cause described above. Then restart the appliance using the reset button. If the message comes back, a part usually needs replacing or the fault needs to be repaired by a qualified professional.
Which parts do I need for Viessmann fault code 402?
That depends on the exact cause. In the Viessmann parts overview at Instalpunt you will find the current price and stock for each part.
Can I fix fault code 402 myself?
You can reset the appliance and check things like the water pressure or settings yourself. Work on gas-carrying parts must be left to a certified gas engineer.
All Viessmann boiler faults and codes at a glance →