In an earlier contribution to this discussion,
Darren Griffin - PocketGPSWorld wrote:

geoff wrote:
Do you have a wire trapped somewhere?

Is there water damage on the board?

What happens if you disconnect the pump?

No obvious signs of damage on the PCB, no arcing, burns or any water
damage ceratinly. If I disconnect the Pump supply from the PCB (fan
is now reconnected) I no longer get any blown fuses, Boiler ON light
illuminates but I have left the thermostat OFF.

Appreciate your help here, I assume this means the fault points
towards the pump and I should be looking in the airing cupboard now?

Probably. You could bottom this out by disconnecting the pump from its
current supply (junction box, or whatever) and putting a 13amp plug with 3
amp fuse on the end of its lead. Plug this into a 13amp socket (with the
help of an extension lead if necessary) and see what happens. If the fuse
blows, it's pretty conclusive.
--
Cheers,
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