Potterton Suprima 80 HE - help please!

I'm at my elderly parents for Christmas and their boiler is playing up. They haven't been able to get someone out so I've had a look at it to see if we can get some heat in the house.

The boiler is locking out and then resetting itself in a constant cycle. The flashing lights indicate a circulation fault which, if I've read to manual correctly, indicates that the casting thermister is reporting an overheat condition.

I followed the troubleshooting flow chart for this fault - one of the steps was to determine if there was 240v being switched to the pump when the lockout occurs. There was power being sent to the pump so, in line with the manual, I replaced the pump. No joy.

My Dad then mentioned that he had a spare control board from when he last had problems with the boiler (it turned out to be something different that time round so he kept the new baord). I switched the control boards but no joy.

I have a temperature probe on the flow pipe right by the casting - I only measure about 40 celcius before the lock out occurs.

Could it be the casting thermister? I measure 13.9k ohms across the sensor at room temperature.

Any help would be gratefully received!

So I got hold of a new casting thermistor and swapped it out - no joy, the boiler is still tripping out.

Any ideas anyone? Cheers...

Dont throw any more bits at your parents boiler, get a boiler repairer to er repair it, because the fault is related to one of the safety devices (I think) you wont get much help from the forum.

It might be a restricted flow rate from the pump.

But that would need the flow and return temperatures to be checked.

I never believe there statements "not been able to get anyone". I have heard that said by people within five miles of me.

I am sure if you give your postcode that there will be someone here close enough to go to repair it ( providing they have not put their feet up early )

Tony

Also intreagued about replacing the pump.

Was the original pump turning?

What made you think it was faulty?

Tony

Thanks for the replies. It turned out the be the thermister on the flow pipe - a new one fitted and all is good. It seems the boiler was reporting the wrong error via the flashing lights.

I replace the pump as I followed the fault finding flow chart provided with the boiler - this said to replace the pump. Pumps are cheap and easy to fit so I took a punt. It didn't work out but I fitted the old pump in my house to replace a very noisy one so not all was lost.