Potterton blowing fuses

14 Feb 2004
Reaction score
United Kingdom
I have a Potterton Suprima 40. It keeps blowing the fuse in the FCU. The fuse on the PCB is OK. The boiler powers up when I disconnect the overheat thermostat, but it will not ignite.

The overheat thermostat is a dead short , so I guess that it is faulty. There must be a short somewhere else as well. I guess it might be the PCB.

Any help appreciated.
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The overheat stat is SUPPOSED to be a dead short until it gets to 95 or so!


Could be a motorised valve, pump, gas valve...
Chris R, Thanks for the reply. I checked for shorts in the wiring and on the valve etc. and could not find any. I removed the PCB and found some discolouration on the traces. I read the fault finding guide again and realised that the overheat stat is supposed to be closed. The fuse only blew when the overheat stat was connected

I bought a new PCB.

Boiler now working.

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