Your boiler’s solar heating connection has a faulty sensor that is incorrectly detecting a short circuit, preventing your solar panels from helping to heat your water.

Control mode - Solar: Sensor S3 shorted out

What causes this fault?

This fault occurs when the electrical resistance in the solar temperature sensor falls outside of its normal range, signaling a short circuit to the boiler. The most common reasons are internal failure of the sensor itself or physical damage to the wiring, such as water ingress or frayed cables, which prevents the system from accurately reading the solar tank temperature.