Oilski, you're a brick! Thanks VERY much.
It was indeed this pressure_switch_lever_microswitch you speak of,
so the problem is now SORTED. :D
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Thanks also for your comments, Agile/Tony.
I DO KNOW that a charge would quite rightly be made for a...
Re-reading the original I see the "mate" is actually a "she".
So looks like she was suffering from "hot flushes"!
(Actually, for a day or two in about 1978, an office block in Central London was using HOT water for flushing the WCs and urinals. I still dunno why!)
Thanks for your contribution, Slugbaby, it's always worth checking the simpler possibilities first as per your suggestion.
I have difficulty "reading" the diagrams, but will try to plough through the manual.
Meanwhile, the pump runs (or appears to run), provided the control is set to...
Installed c1988, was working OK through March 2006.
DHW still works OK, but at recent gas safety check the
engineer noticed that it does not respond to Central Heating
demand. However, he is unfamiliar with Leblanc kit.
Have user and installation manuals, but not obvious.
Pump does...
coldfused should check that the thermo/mano is firmly clipped in place.
On our GVM 4.20 the reading was approx zero even though the system was obviously pressurised and holding its pressure, but I later discoverd that the gauge had been pushed slightly sideways maybe by adding or removing the...