thermistor

Hi All, Just hoping someone might have an idea on this. The boiler is running fine in terms of hot water but stopped running the Central Heating when called for from the Hive (It's sending a Live feed to the boiler from the Hive so thats all good.) We thought it might have been a PCB problem so...

Good evening all, I hope someone can help. I have a PulsaCoil 3 that may or may not be on its last legs. The manual tells me that a flashing red LED on the circuit board means a 'pumped return thermistor failure'. Unfortunately I can't seem to find out where the thermistor is or even what it...