Fridge runs constanly

Hello to all

As stated above my fridge runs all the time. Recently I discovered that the condenser in the freezer compartment had iced up. So I defrosted the unit for several hours cleaned all of the ice out, vacuumed the coils, and compressor area. All was fine, the fridge temps is at 37 deg. F, and the freezer is -10 deg. F.
Even though the temps are good, the unit continues to run.
Any suggestions?

Thank You
Mitch

Here are your parts
http://www.appliancepartspros.com/partsearch/modelsearch.aspx?model=FRT18S6ABL

I am assuming the unit’s thermostat is set to mid-scale.
Your freezer temperature is actually too cold. It should be between 0 and 5 degrees f so the unit runs all the time trying to achieve a lower freezer temperature.
Sounds like the thermostat (Item 21 in Section 3) is not opening anmd should be replaced.

You may also have a defrost problem (re: iced up evaporator coils) but I cannot say for sure.