Water boiler problems ... (longish)

... no, not sort we usually talk about here, I mean the ones for boiling water to make big pots of tea !!
I have been asked to "take a look at" four catering style water boilers which are apparently faulty. I have inspected two of them so far and am mildly puzzled ..
On both boilers, the heating element appears to have four wires connecting to it, but on close inspection (and a poke around with the trusty old Avo) only two connect with the resistive element. The other two wires connect to something that I'm guessing is a temperature-sensitive switch that will open if the element gets too hot - like if the unit is switched on with no water in it!
Neither boiler was working on arrival, but now both of them seem to be operational again. The only thing I believe I have done to "repair" (!) them is to poke about at the little 'protective switches' - if that's what they are. Both of them seemed to have a little bit sticking up in the middle - about 3/16" long and the diameter of a pencil lead - looking as if it's made of ceramic. Figuring that this might be a "reset" toggle, I poked it with the prod of my test meter, and although it didn't *appear* to move at all, the boiler has myseriously started working again (indeed, both of them have after the same treatment).
So .. are those little thingies over-tempreature cut-out switches as I am presuming them to be? And are they "resettable" by means of pressure on the little spike in the middle? And if they *are*, but they *have* been triggered by over-temperature, is my 'reset' a short term thing that won't last and the switches need replacing? Or can the boilers now be put back into service?
Incidentally, although both boilers are rated at 3 Kw, one of them has a relay to interrupt the current through the heater, and the other does not - all the connections go to the "temperature control" that has an external rotatable knob. In the case of the one with the relay, the presumed overtemp cutout switch is wired in series with the relay energising coil. On the other unit, the 'switch' is wired directly in series with the heater. The manufacturer has a web site, but it (predictably) contains no useful information if you want to do anything other than buy a new product.
So many questions, so little time ...
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And no useful information as to who makes the boiler
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geoff

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writes

Correct. They are manufactured by Lincat Limited, but as I mentioned, I did not find any helpful information on the company website. Now it's no longer Sunday, I guess a call to their Service line might be appropriate ...
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