potterton suprima - pcb or something else?

[graham]

I've read the ovation for this boiler's circuitry on this newsgroup, but before I leap into replacing the pcb on mine I'm wondering if there's something else causing the problem...

Symptoms are: every so often, while there is demand for heat the boiler stops; the green light flashes ~twice a second, sometimes the red light is on, sometimes off.

When the thing is in this state the water pipes coming out of the top aren't paticularly hot. Resetting may result in the thing firing, then after a few seconds it goes back to the previous state. Left alone it eventually starts working again. I checked the heat sensor and it didn?t have a particularly low resistance.

So I'm thinking it's probably the notorious pcb. Before I replace it can anyone think of anything else I should check?

thanks,

graham.

[Ed Sirett]

I presume that the temperature knob is set more than half way on? This is what the boiler would do if it reckons that the primary water is hot enough. So it could be the PCB or it could be the sensor is wrong - but since you tested it and the fault is intermittent I'd go for the PCB.