[raytronx]

It's a resistor that changes resistance with temp, so called a Thermistor.

The change in resistance is read by the little fridge brain and adjusts the amount of heat applied to the boiler and cools the fridge more. Moving the thermistor higher makes it cool more. I believe the air is warmest near the top, hot air rises, so there is a temp difference.

It's a pretty smart simple method, no moving parts, unlike a knob method which can get oxidized and easily get erratic.