Vaillant fault code F.27
Fault code F.27 on a Vaillant boiler (including Hrpro and ecoCOMPACT) means: Incorrect ionisation measurement. 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.27 on a Vaillant boiler indicates: Incorrect ionisation measurement.
Applies to
Vaillant Hrpro, ecoCOMPACT, ecoFIT pro, ecoTEC classic, ecoTEC exclusive, ecoTEC plus, ecoTEC pro classic, ecoTEC pure, CW 4/3, CW 4/4, CW 4/4 EXP, VC 1006/5-5 R3, VC 1206/5-5 R3, VC 806/5-5 R3, VHR 18-22/3 C, VHR 18-22/3-5.
Fault code F.27 on other Vaillant series
The same code does not mean the same thing on every series. Check the rating plate to see which series you have:
- F.27 on ThermoCompact, VCW 255/2 E: Ionisation signal with closed gas valves.
- F.27 on ThermoCompact, CWK 245/3, CWK 245/3 R1, VCW 254/3, VCW 255 E, VCW 255/3: Incorrect ionisation signal.
- F.27 on Hrpro, ThermoCompact, CW 3/3, CW 4/3 EXP, VC 254/4-7, VCW 254/4-7: Safety shut-down: flame simulation.
Matching parts
Vaillant parts are available from Instalpunt; shipping to EU countries from €17.95 (€24.95 for more distant countries), usually 3–5 working days.
Parts by Vaillant series: ecoTEC plus · ecoTEC pro.
For fault code F.27, the part involved is usually in the category: electrode.
This message does not point directly to one faulty part. These are the parts that most often fit this appliance:
- Vaillant pressure sensor VHR18-22/3C24-28/3C VHR CW3 4/3 for ecoTEC plus and ecoTEC pro etc. € 24.18
- Vaillant ignition pin gasket VHR for ecoTEC plus and ecoTEC pro etc. € 7.19
- Vaillant NTC sensor flow/return VHR18-22/3C24-28/3C for ecoTEC plus and ecoTEC pro etc. € 16.99
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 Vaillant boiler fault code F.27 mean?
Incorrect ionisation measurement.
How do I fix fault code F.27 on a Vaillant 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 Vaillant fault code F.27?
That depends on the exact cause. In the Vaillant parts overview at Instalpunt you will find the current price and stock for each part.
Can I fix fault code F.27 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 Vaillant boiler faults and codes at a glance →