"David Billington" wrote in message
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I remembered this problem when a friend complained that the Cal
Controls controller on her glass furnace was giving thermocouple
failure faults. Various people had said to buy a new controller but
as I have a Cal controller I was aware that the guts of the
controller can be prised out of the panel mount enclosure, I presume
to allow easy replacement when banks of them are fitted such as in
plastic extruder lines. As I had mine apart to fit a comms module I
was aware the PCB contacts were just tinned and might suffer this
problem possibly causing issues with low level signals such as the
thermocouple. I made a small pry bar to get the guts out and
re-inserted it a couple of times and the problem went away. I've had
the same happen on my controller more recently and removing and
refitting it cured the fault.

I have a nice 5-channel thermocouple temperature display in the
kitchen that I bought real cheap, and then found that it
intermittently went haywire until firmly rapped. Un- and re-plugging
everything has fixed it. The culprit was likely a socketed 40-pin IC.
http://www.doric-vas.com/400.htm

Now I can tell that a cooking pot on the woodstove downstairs has
reached boiling before I smell it burning.