Error code
Vaillant Boiler Fault Code F64
Quick answer
F64
A boiler sensor is giving an invalid reading
First safe action
Consult the manual for any user guidance specific to this fault.
Meaning
Vaillant boiler fault code F64 usually means the boiler is receiving an unexpected reading from one of its temperature or system sensors.
Likely causes
- Faulty sensor
- Wiring issue
- Control board not interpreting the sensor correctly
Safe first checks
- Consult the manual for any user guidance specific to this fault.
- Use only the standard reset process if it is intended for homeowners.
- Stop if the code reappears immediately.
How to reset
- Carry out one standard user reset if the manual allows it.
- Arrange professional diagnosis if the sensor fault remains active.
When to call an engineer
If the code remains after one standard reset, a qualified heating engineer should inspect the boiler.
Safety warning
Do not remove the boiler casing or handle internal wiring or sensor components yourself.
Useful hub links
Related fault codes
F62 for Vaillant Boiler
Gas supply control or gas valve issue
F65 for Vaillant Boiler
The boiler has overheated or hit a high temperature limit
F72 for Vaillant Boiler
A boiler sensor is giving an invalid reading
F83 for Vaillant Boiler
A boiler sensor is giving an invalid reading
F54 for Vaillant Boiler
Gas supply control or gas valve issue
F61 for Vaillant Boiler
Gas supply control or gas valve issue
Relevant guides
Frequently asked questions
Can I keep resetting a Vaillant boiler with F64?+
No. If F64 returns after one standard user reset, stop there and arrange a qualified engineer if the manual gives no safe next step.
Is F64 something I can repair myself?+
Boiler faults should be treated cautiously. Stay within the user checks in the manual, and leave gas, combustion, and internal boiler repairs to a qualified professional.