Viessmann fault code F Ab
Fault code F Ab on a Viessmann boiler (including Vitocrossal 300) means: Air pressure switch defective, incorrectly connected or incorrectly set. 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 F Ab on a Viessmann boiler indicates: Air pressure switch defective, incorrectly connected or incorrectly set.
Applies to
Viessmann Vitocrossal 300, -.
Click a model for the parts list and exploded view of that appliance.
Fault code F Ab on other Viessmann series
The same code does not mean the same thing on every series. Check the rating plate to see which series you have:
- F Ab on Vitocrossal 300, -: Flue gas blockage, condensate blockage.
- F Ab on Vitocrossal 300, -: Fan defective, cables defective or open circuit.
Matching parts
Viessmann parts are available from Instalpunt; shipping to EU countries from €12.95 (€16.95 for more distant countries), usually 3–5 working days.
This message does not point directly to one faulty part. These are the parts that most often fit this appliance:
- Viessmann siphon Vitocrossal 300 € 35.28
- Viessmann inspection hatch gasket vsb 72/89 gf 10x10 l=700 mm € 44.43
- Viessmann flue gas gasket 2nd heat exchanger Vitocrossal 300 720kW € 95.40
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 F Ab mean?
Air pressure switch defective, incorrectly connected or incorrectly set.
How do I fix fault code F Ab 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 F Ab?
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 F Ab 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 →