Ariston eurocombi boiler not firing up. Thermostat lights all on upto 80 degrees as if overheating. Pressure fine. No fan, no ignition.

The fault occured a few days after I altered the radiator layout and then refilled the system. Intially the boiler worked fine, then a few days later all of the temperature lights light upto 80 and the boiler would not fire. The pump was working but the fan was not. After diagnosing the electronics I came to the conclusion it was either the contol pcb or the temperature probe. As the temperature probe was the cheaper option I replaced that first. The system is now working again. I think this fault was caused by me failing to completly remove all air from the system after refill and an air lock occuring causing the probe to burn out.