My refrigerator was giving problems and i also thaought it was some sort of dial of fan that is what the engineers from the service company kept telling us but everytime they left after replacing parts the problem would occur months later. It's one of those german refrigerator liebherr. Contacted liebherr who put me in contact with http://www.agsrefrigeration.co.uk. who attented and replaced one of the sensors which was controlling the freezer fan. It did't have a thermostat it was control by a pcb module.