F.00
FAULT CODE
Vaillant
Flow Temperature Sensor Interruption
High Severity
Engineer Required
The flow NTC (Negative Temperature Coefficient) sensor has an open circuit or broken connection. The sensor monitors flow temperature and is essential for safe operation.
Step-by-Step Fix Guide
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Step 1
Turn off the boiler at the programmer/thermostat
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Step 2
Do not attempt to open the boiler casing
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Step 3 Engineer only
Call a Gas Safe registered engineer to test and replace the NTC sensor
Gas Safe Reminder
Work on gas appliances must be carried out by a Gas Safe registered engineer. The steps above cover safe checks a homeowner can perform - any internal component replacement requires a qualified professional. If in doubt, always call an engineer.