Hi Dan, thanks for the reply.
Went back to recheck the voltages and the 150 volts to the fan had disappeared!
I then checked the voltages across Pin 11 and Pin 8, no volts??
I removed the controller and lifted off the plastic covers and found that the pcb was badly scorched around Relay...
I am round at a house of a young lady in Sussex and she has been without central-heating or hot water for 2 weeks! I have sorted the hot water using the electric immersion heater (on for 2 hours a day).
Removed covers and notice that the Halstead Best 50 has a fan which does not start when...