A Vaillant boiler that’s not turning on is not ideal, but many modern appliances are designed to ‘lockout’ when there’s a fault or risk for your safety. There could be unsafe conditions to keep operating such as a bad supply of gas, or a fault in the system.
Resetting the Vaillant Boiler
To reset the Vaillant boiler manually, press the reset button (3) and hold for one second.
Possible reasons for a lockout-
- Water pressure
- Ignition failure
- Heat exchanger blocked
If you are unable to resolve the ignition problem yourself by resetting the boiler three times, then consult a professional.