What is the voltage for the evaporator fan for lg mod # lrbn20512 is it 115 volts ac or a low voltage fan motor 18 to 20 volts ac

Physically Obstructed If the fan is not running, unplug the refrigerator and remove the evaporator fan cover. In many cases the problem is do to the fact that the evaporator fan cannot operate freely due to an ice buildup on the fan blades. Sometimes one or more of the fan blades, in the case of fans equipped with metal blades, have become bent causing it to jam against the metal fan shroud. In the case of ice buildup, simply allowing the ice to melt away will cure the problem as long as the motor windings have not been damaged. If the problem is bent fan blades, replace the fan blade. Do not try to straighten the blade because it will be out of balance. Sometimes the problem is a buildup of dirt in the motor bearings and a good shot of penetrating oil can solve the problem...
Replacing a Defective Fan Motor Evaporator fan motors draw very little current and have a long life-cycle, but they can burn themselves out if their fan blade becomes jammed and unable to rotate. If the fan blade rotates freely, but the fan does not run, disconnect the fan wires at the fan and check for continuity through the motor windings using digital or analog multimeter. If you get no continuity through the winding, the winding is bad and you need to replace the fan motor assembly. The fan is usually held in place by three or four screws. Simply remove the old fan and take it with you to the appliance parts store to get an exact replacement. Check for Voltage If the fan motor checks out OK physically and electrically, check to see if there is voltage present at the fan motor's terminals. To check for the presence of voltage, set your digital or analog multimeter to its AC voltage function and attach the test leads using alligator clips. Position the test leads so the clips do not touch each other or the refrigerator cabinet. Plug the refrigerator in and note the meter reading. It should read 120 volts. A reading of zero volts means that there is no voltage reaching the fan motor. Unplug the refrigerator again before continuing the troubleshooting.. Bad Thermostatic Control No voltage reaching the fan motor could be caused by a broken wire between the fan motor and the thermostatic control, but broken wires are rare. To check for a broken wire, remove the thermostatic control from the refrigerator cabinet and take continuity reading between both ends of the wires. If the wires check out OK, replace the thermostatic control. Take the old one to the parts store with you to get an exact replacement.

The fan on this model is only 12 volts. Make sure that is what your replacement is rated.

If the evaporator tube is iced up entering the coil and cool to warm leaving the evaporator, that would indicate low on refrigerant or a restriction. If it is iced up entering and leaving the evaporator, then, it could be low on refrigerant,blower not running at proper speed, dirty evaporator coil or filter.
You need to check the suction and head pressure and temperature to determine problem for sure.

There is one compressor that serves both the freezer and refridgerator compartments. You need to confirm if the evaporator fan in the freezer compartment is working. When you open the door to the freezer, you should see and hear the evaporator fan in the freezer compartment running. Particularly if there is a demand on the unit through the thermostat setting. If the evaporator fan is not operating, you can check the evaporator fan motor with a volt meter to see if it's getting power. If its getting voltage, but not operating, you need to replace the evaporator fan motor in the freezer compartment. There are 3 wires that attach to the evaporator fan motor. One hot wire, one neutral wire and one ground wire. The ground wire is usually marked green, the voltage wire is usually marked black and the common wire is usually marked white. You should get a reading on your volt meter of a voltage from the hot post to the neutral or from the hot to the ground. If it is getting power but will not operate, then it is definitely a bad fan motor that would need to be replaced.

There is one compressor that serves both the freezer and refridgerator compartments. You need to confirm if the evaporator fan in the freezer compartment is working. When you open the door to the freezer, you should see and hear the evaporator fan in the freezer compartment running. Particularly if there is a demand on the unit through the thermostat setting. If the evaporator fan is not operating, you can check the evaporator fan motor with a volt meter to see if it's getting power. If its getting voltage, but not operating, you need to replace the evaporator fan motor in the freezer compartment. There are 3 wires that attach to the evaporator fan motor. One hot wire, one neutral wire and one ground wire. The ground wire is usually marked green, the voltage wire is usually marked black and the common wire is usually marked white. You should get a reading on your volt meter of a voltage from the hot post to the neutral or from the hot to the ground. If it is getting power but will not operate, then it is definitely a bad fan motor that would need to be replaced.

There is one compressor that serves both the freezer and refridgerator compartments. You need to confirm if the evaporator fan in the freezer compartment is working. When you open the door to the freezer, you should see and hear the evaporator fan in the freezer compartment running. Particularly if there is a demand on the unit through the thermostat setting. If the evaporator fan is not operating, you can check the evaporator fan motor with a volt meter to see if it's getting power. If its getting voltage, but not operating, you need to replace the evaporator fan motor in the freezer compartment. There are 3 wires that attach to the evaporator fan motor. One hot wire, one neutral wire and one ground wire. The ground wire is usually marked green, the voltage wire is usually marked black and the common wire is usually marked white. You should get a reading on your volt meter of a voltage from the hot post to the neutral or from the hot to the ground. If it is getting power but will not operate, then it is definitely a bad fan motor that would need to be replaced.

you check the fan motor and the compressor winding and terminal you have a short

Unplug the wires from the motor and check the voltage differential cross the two wires. If you have 120 Volts or in that area the motor should run. Try moving the fan shaft up and down. If you have any play in this the motor bearing are bad. Replace the motor.

Your fan motor is bad cause you have the voltage input to your fan motor but still the motor is not operating. May be the motor winding is open, check the white and red resistance.