F.72 — Flow/return NTC fault

What does F.72 mean?

The boiler has detected an implausibly large temperature difference between the flow and return NTC sensors, suggesting one or both sensors are faulty.

• Flow temperature sensor is defective.
• Return temperature sensor is defective.
• Both flow and return temperature sensors are defective.

Click steps to track your progress.

1. 1

   Press the fault clearance key on the boiler to reset it.

2. 2

   Observe if the boiler runs normally for a period before the fault reappears.

3. 3

   If the fault persists, contact Vaillant Service Solutions to diagnose and replace the faulty sensor(s).