Posts by Tim Wilson

Vaillant boiler error codes are the diagnostic messages your boiler displays whenever it detects a fault, whether that’s low water pressure, an ignition failure, a sensor issue, or a genuine…

Vaillant’s own manual describes the F27 fault code as a safety switch-off caused by flame simulation, meaning the electronics have picked up what looks like a flame, or a flame-like…

If your Vaillant boiler has locked out showing F25, it’s warning you that the temperature of the gases leaving through the flue has climbed higher than it safely should, or…

The Vaillant boiler F28 fault code means the flame signal was not detected during the ignition phase, so the control board shuts the gas valve and locks the boiler out…

The Vaillant boiler F23 fault code is a safety switch-off triggered when the difference between the flow and return pipe temperatures exceeds roughly 35 degrees Celsius, which tells the boiler…

The Vaillant boiler F61 fault code is a gas valve actuation fault, meaning the printed circuit board cannot drive or confirm the gas valve correctly, so the boiler shuts down…

The F22 fault code is a low water pressure safety lockout, meaning your Vaillant boiler has detected that there isn’t enough water in the sealed heating system to circulate and…

The F26 fault code means your Vaillant boiler’s gas valve isn’t functioning as it should, most often because the stepper motor that drives the valve has failed, disconnected, or is…

The Vaillant boiler F76 fault code means temperatures inside the heat exchanger have risen well beyond safe operating limits, typically somewhere above 95 to 105 degrees Celsius, causing a dedicated…

A faulty diverter valve on a boiler is most commonly caused by wear and tear over time, limescale buildup, debris or sludge in the system, a stuck or seized valve,…