Refrigerator and freezer are cold but no fan is running

There is a t-stat that controls that fan in the freezer. Sometimes it is combined with the defrost terminator and others it is alone. You need to thaw out freezer and look for it after removing the plastic cover. The t-stat is round with two or three wires and connects to the fan. If not that the fan is bad. The only way to know is to check them with an ohm meter. If the fan shows continuity then the t-stat is probably bad. A t-stat with two wires is easily checked: put it in a freezer for about 30 min and if there is no continuity it is bad, or just eliminate it from the circuit and if the fan runs you have found the problem. Make a jumper and run the fan without the t-stat until you can get a new one. It makes very little difference anyway. DrTom4444