Low pressure indication shuts off heater

As new to this forum, I have just found a way back in to the answer to my ‘low pressure indication’, question from Alistair, for which many thanks. I thought that I had posted a follow-up question yesterday, but as it has not appeared I will try again.

Alistair is correct in that it is a faulty PCB – to be more precise, the button switch at the bottom, which was gunged up with what looks like brown resin, although I don’t know where it came from. I have cleaned some of it off, but the switch still does not work and I can’t see the actual contacts inside the switch – I may try a bit of heat to melt the resin. Presumably the switch by itself is not available? Anyone got a duff board with a good switch?

The switch contact appears to be normally open and closed by the pressure paddle, so I will short the switch to prove the fault. If this does the trick, I am inclined to leave it like that! (The alternative being a £56, 10.5kW board.) Genuine low pressure is infrequent and hopefully would only result in some extra hot water, or at worst a damaged control PCB.

(As an aside, some time ago a plumber fitted an electric shower for a friend of mine which, when switched on, melted the solder on the boiler. He fitted another one and it did the same. It was only when I pointed out that he had got the inlet and outlet pipes reversed that the third one worked!)