Potterton Suprima 80e running continuously

[intamixx]

Hello,
I have a potterton suprima 80e boiler. The pump stopped working last week blew the fuse on the main pcb board. I replaced the fuse on the pcb board and it kept on blowing the fuse. We replaced the pump for another one and the pcb started working ok, but did the boiler flame did not ignite and it kept going into lockout mode (red led flashing). We replaced the pcb board and the thermistor and over heat stat was replaced at the same time. The boiler then started to ignite and thought was ok.
Usually when the boiler runs a heating cycle for a couple of hours, it turns itself off to cool and then turns back on to prevent overheating. However, now the boiler runs continuously to the point where it gets so hot (we can hear the fan really whurring around) that it locks itself out after about an hour to stop itself from overheating. So basically its not turning itself off to cool off during normal operation and then back on.
Is this because the over heat stat was not put in correctly or is this because the replaced thermistor is not functioning correctly? Is there anything I should check first?
Any advice would be most appreciated.
Thanks.

 

[Agile]

If I remember correctly the boiler stat has an NTC thermister on the end of thin wires.

But to respond properly the pocket the NTC goes into has to be filled with thermal conduction paste.

You can buy that for computer processors.

But if caught out some silicone grease will do a temporary job.