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.
Possible reasons for a lockout-
- Water pressure
- Ignition failure
- Heat exchanger blocked
Resetting your Vaillant Boiler
- To reset the boiler manually, press the reset button (3) and hold for one second.
If you are unable to resolve the ignition problem yourself by resetting the boiler three times, then consult a professional.