My refrigerator the evaporator keep freezing , i had clean out the ice ,but after 2 , 3 week it freezing again , can please let me know . my refrigerator model-gsh25jstass

GE refrigerators are subject to a blown defrost heating element and thermostat.
Unplug the refrigerator,remove the freezer shelves. Remove the back wall of the freezer to access the defrost thermostat and defrost heater.
The heater is glass. It will have a dark burned appearance. The heater and thermostat both should be replaced. They come as a set.

Pull the refrig out and remove the 8 " x 10 " panel . Behind this panel , is the main control board ( you already know , since you changed it ) . Unplug the refrig . Remove the BLUE plug from the board , with 3 larger wires going to it . Looking at the blue plug , the sequence will be wire1,wire2,space,wire3 . Get a short piece of insulated wire , and strip about 1/4 inch from each end . Insert 1 end into wire2 , and the other into wire3 . Plug the refrig back in . After about 3 min , look in the freezer , at the bottom , behind the crisper , look for a red glow . If no red glow , unplug the refrig , and reassemble the plug and cover . This no glow , indicates a shorted defrost heater ( pt. number WR51X10055 ) . It is also advisable to replace the defrost thermostat ( pt. number WR50X10068 ) when replacing the heater . To access these parts , you will have to remove the inside rear wall of the freezer . The heater , is at the bottom of the coils , held on with 2 screws , and the thermostat , is the 1 " cylinder , with a blue and pink wire going to it , clipped on the top left of the coils .
If you do get a red glow , then the # 4 thermistor is bad . This tells the main control board , the temp of the coils , if they need defrosted , when they are thru defrosting . This thermistor is the 1 " long , torpedo looking piece , clipped on the top left of the coils , with 2 white wires going to it . Part number WR55X10025 . It would be advisable to also replace the # 5 thermistor , located at the bottom of the freezer , slightly in front of the drain , also with 2 white wires going to it , slid into a housing . This thermistor , is the freezer thermistor , which tells the control board , the freezer temp , when to cycle off , associated with the fan speed also .