I have a G.E. refrigerator. I thank the model # is

1- Bad Defrost Heater 2- Defrost Bimetal 3- Freezer sensor, or 4-Bad Control Board.

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 WR51X10101 . 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 .