Got s20drbb32ag tested seemed to work ok for hour or two then noticed not knocking off at temp inserted thermometer into freezer got down to -31 degrees still running no change on display suspected temp sensor? or control board ? temp sensor 30 quid control board 150 quid.Have you got any resistance values to check temp sensor is it ptc or ntc as it disappears into insulation new one seems to be an add on inside cabinet