Bottom part won't get cold and motor keeps running

First of all check your freezer for excessive frost on the back panel. If you have excessive frost then your evaporator is probably ice up which means one or more of a few problems. They are possibly:

1. First a possible defrost timer problem. To check you will find the timer either at the bottom in front behind the grill (sometimes called the kick panel) or in back behind the back cover. When you find it turn the small dial clockwise until you hear it click. When it click you should hear a hissing sound coming from your freezer which is the heater coming on (you may want to remove the evap. cover in back of the freezer compartment so you can hear it better you will have to have it off to perform the other checks anyhow). If the heater comes on the timer needs to be replaced. If it's okay advance the timer until (if it is running) the evap. fan comes back on.

2. Check and make sure your evap. fan is running. It is the fan above the evap. that you see when you remove the panel. If it is running it's probably okay. If not check for 125V if it is not running and you have the needed voltage replace it. If it is running then check the heater and make sure you have continuity through it. You should get a reading when you register across the outer leads. (you will need to disconnect the heater to check as well as the evap. thermo.) If it shows no reading replace it.

3. Next check the defrost thermo. If your freezer is not frosted up you won't get a reading through it. If it is and you don't get a reading then replace it.

Hopefully this will help.
Good Luck!
God Bless