Vaillant fault code F.09
Fault code F.09 on a Vaillant boiler (including hrSOLIDE) means: Domestic hot water sensor. Reset the appliance once. If the code comes back, a part is usually faulty, often a temperature sensor. 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.09 on a Vaillant boiler indicates: Domestic hot water sensor.
Fixing fault code F.09: step by step
- Reset the appliance once; a one-off measuring error will then clear.
- Where you can reach it without opening the sealed combustion section, check that the sensor plug is seated firmly and the wiring is undamaged.
- If the code comes back, the sensor or its wiring is usually faulty (short or open circuit). Sensors in the sealed combustion section should be replaced by a qualified heating engineer.
Applies to
Vaillant hrSOLIDE, VHR 10 S, VHR 18 S, VHR 18-22 C, VHR 24 S, VHR 24-28 C.
Fault code F.09 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.09 on HRV, HRV 24: Water pressure sensor broken or wiring faulty.
- F.09 on ecoTEC classic, VHR 18-24/5-3 EXP R6, VHR 18-24/5-3 R6, VHR 23-28/5-3 EXP R6, VHR 23-28/5-3 R6, VHR 28-34/5-3 R6: Short circuit or open circuit of domestic hot water sensor.
Matching parts
Vaillant parts are available from Instalpunt; shipping to EU countries from €12.95 (€16.95 for more distant countries), usually 3–5 working days.
Parts per Vaillant-series: ecoTEC plus · ecoTEC pro.
For fault code F.09, the part involved is usually in the category: sensor.
Based on the cause, these original Vaillant parts fit (always check the type number of your appliance):
- Vaillant NTC sensor flow/return VHR18-22/3C24-28/3C for ecoTEC plus and ecoTEC pro etc. € 17.67
- Vaillant sensor cable for ecoTEC pro € 18.35
- Vaillant pressure sensor VHR18-22/3C24-28/3C VHR CW3 4/3 for ecoTEC plus and ecoTEC pro etc. € 25.15
Further reading on this cause
Other Vaillant codes with the same cause
- F.00 — Open circuit of flow temperature sensor
- F.01 — Open circuit of return temperature sensor (NTC)
- F.02 — Open circuit of DHW outlet sensor
- F.03 — Open circuit of cylinder temperature sensor/domestic hot water temperature sensor
- F.05 — Open circuit in outdoor temperature sensor
- F.06 — Open circuit of inside flue gas sensor
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.09 mean?
Domestic hot water sensor.
How do I fix fault code F.09 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.09?
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.09 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 →