When delivered, the control had to be turned all the way to "5" - the highest setting - to get it to control in the safe range, as measured by a refrigerator thermometer.  We left it set at "4" for days but it wouldn't cool below 40 degrees.  It seems capable of operating at a proper temperature, since it only runs for about 10 minutes out of an hour.  A service man came out and concluded that it needed a new thermostat.  We're still waiting for installation of the thermostat.