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Vaillant Boiler F.13 Error Code
Hot water cylinder sensor short circuit on Vaillant boilers.
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The sensor that reads the hot water cylinder or store temperature has shorted out. Vaillant puts it down to the sensor's wiring connection or a faulty sensor.
Compatible models
Listed on Vaillant's UK fault code page without a model list; it applies to boilers with a hot water cylinder or store sensor. The ecoTEC plus VU ..6/6-5 OVZ manual lists it as the DHW cylinder sensor short circuit.
Also shown as
No other codes are listed for this fault.
Difficulty
Try the basic checks, but the usual fix is a technician's job.
Not sure you are reading the code right? See how to read Vaillant boiler codes.
How to fix Vaillant F.13
Restart the boiler
Switch off for a minute and back on. If F.13 comes straight back, book a visit.
When to call a technician
A Gas Safe engineer (or the installer who fitted the cylinder) needs to test and replace the sensor.
Parts linked to F.13
These are the parts an engineer usually checks for this code. They sit inside the sealed casing, so leave them to a Gas Safe registered engineer.
Frequently asked questions
Which Vaillant models show the F.13 code?
Listed on Vaillant's UK fault code page without a model list; it applies to boilers with a hot water cylinder or store sensor. The ecoTEC plus VU ..6/6-5 OVZ manual lists it as the DHW cylinder sensor short circuit.
Can I fix Vaillant F.13 myself?
Only the outside checks. The steps above are the ones Vaillant's user instructions allow; if they don't clear F.13, the fix is inside the boiler and needs a Gas Safe registered engineer (RGII in Ireland).
Other Vaillant boiler codes
- F.22Water pressure in the heating system is too low
- F.28Boiler failed to light
- F.29Flame went out and the boiler couldn't relight
- F.20Overheat safety cut-out has tripped
- F.23Too big a gap between flow and return temperature
- F.24Temperature rising too fast
- F.25Flue gas temperature too high
- F.27Flame detected with the burner off
- F.75No pressure rise when the pump starts
- F.00Flow or return temperature sensor not reading
- F.10Temperature sensor short circuit
- F.32Fan speed out of range
- F.61Gas valve control fault
- F.62Flame took too long to go out
- F.68Unstable flame
- F.70Invalid device code after a repair
- F.83Dry fire: no temperature change when the burner lit
Last reviewed 2026-10-21. Codes and steps can vary by model; check your owner's manual.