On Sat, 09 Feb 2019 09:37:57 +0000, Brian Gaff wrote:

Yes if you can ascertain what the changes in the signal are from the
device,
and measure it, then you know the pot is OK my guess is that the actual
electronics is faulty, for whatever reason, It could even be a
connection to and from the control or sensor, but you need to find the
board and see if its something you can replace. Sods law will dictate
its in the most inaccessible place possible.
Brian

This isn't looking too good. The control unit contains a circuit board.
One of the connectors on the cover is marked "T SENS". There's 4 wires
on the connector, presumably from the fridge and freezer parts. One pair
gives a resistance of 2.85K Ohms and the other 2.95K Ohms. The ambient
temperature is 20C. Is that about what might be expected? I'll put it
all back together and turn the fridge on again and re-measure later to
see if the values change.

There's a photo of the circuit board here but I don't fancy having to
replace components on that. Is there anything I can usefully measure on
the board?

Photo: https://ibb.co/gDrCn82

Kit Jackson