Your boiler has stopped working because the water returning from your radiators has become too hot, which usually means the water isn't circulating properly through the system.

Central heating return temperature is greater than90°C

What causes this fault?

This fault occurs when the water returning to the boiler is too hot, which happens when heat cannot be transferred away into your radiators effectively. The most common reasons are a pump failure that has stopped water from moving, or a blockage caused by a build-up of sludge and debris in the pipework.