Error code
Vaillant Boiler F13 — Code Meaning
Short circuit at the cylinder-temperature sensor. The manufacturer’s UK support table covers several models. Match the exact model and complete code to its manual; this is not proof of identical meanings across every range.
Quick answer
F13: Short circuit at the cylinder-temperature sensor
Meaning
Short circuit at the cylinder-temperature sensor
First safe check
Photograph the full display, including alternating characters and suffixes.
Stop if
The warning remains, the appliance is not operating normally, or the next step requires internal access.
Who to call
Contact a Gas Safe registered engineer qualified for this boiler if the warning remains, the code is not explained in the matching manual, or any internal investigation is required.
Internal diagnosis and repair require a qualified professional. Follow only the model-approved user actions described below. Keep checks outside the casing and use only a manufacturer-approved reset where the manual allows it.
What does this error code mean?
Short circuit at the cylinder-temperature sensor.
The manufacturer’s UK support table covers several models. Match the exact model and complete code to its manual; this is not proof of identical meanings across every range.
The reported condition does not, by itself, establish which part needs replacement.
Why is this happening?
- The manufacturer describes: short circuit at the cylinder-temperature sensor. The underlying cause requires assessment on the actual model.
Safe next steps
- Photograph the full display, including alternating characters and suffixes.
- Record the full model from accessible paperwork or an external label; do not dismantle the appliance to find it.
- Match the source below to your exact model manual before following any code-specific instructions.
- If the warning persists, the model is uncertain or the next step requires internal access, stop and contact a Gas Safe registered engineer qualified for this boiler.
Can I fix this myself?
NoUse only the external checks described here. The code alone does not justify a parts replacement.
Safety boundary: Do not remove the boiler casing or work on gas, flue components, combustion settings or internal wiring.
What not to do
- Do not remove the boiler casing or work on gas, flue components, combustion settings or internal wiring.
- Do not repeatedly reset an unexplained or returning warning, or buy parts solely from this display.
When to call a heating professional
Contact a Gas Safe registered engineer qualified for this boiler if the warning remains, the code is not explained in the matching manual, or any internal investigation is required.
Safety warning
Do not remove the boiler casing or work on gas, flue components, combustion settings or internal wiring.
Useful hub links
Other Vaillant boiler codes
Vaillant Boiler F00 — Code Meaning
Interrupted flow-temperature sensor circuit
Vaillant Boiler F01 — Code Meaning
Interrupted return-temperature sensor circuit
Vaillant Boiler F10 — Code Meaning
Short circuit at the flow-temperature sensor
Vaillant Boiler F11 — Code Meaning
Short circuit at the return-temperature sensor
Relevant guide
Frequently asked questions
Does F13 identify a failed part?+
No. A code describes a reported condition, and the correct model documentation is needed before diagnosis.
Does this apply to every model?+
The manufacturer’s UK support table covers several models. Match the exact model and complete code to its manual; this is not proof of identical meanings across every range.
Sources and review status
Model dependent · Last reviewed 21 September 2026
- Vaillant UK boiler fault-code reference
manufacturer support · UK · checked 21 September 2026
Short circuit at the cylinder-temperature sensor. The manufacturer’s UK support table covers several models. Match the exact model and complete code to its manual; this is not proof of identical meanings across every range.