I have almost the same problem with an Electrolux FREEZER. The alarm lights up but the freezer maintains the right temp. Sometimes the green temp lights flash on and off together. (3 lights =-18deg)
In my case it seems to be an indicator circuit problem that is associated with a low mains voltage. My mains vary from 225 to 240 volts. When the mains are between 230 and 240 volts the problem goes away.
Bob in Galicia, Spain, September 2010