Refrigerator temperature reading?????????

I had a defrost problem and replaced the main control under the freezer cabinet and the defrost thermostat. After installing the new control and thermostat, I put a thermometer in the freezer and one in the refrigerator. The digital display in the refrigerator reads 0 degrees in the freezer and the thermometer reads 0 degrees. However the digital display in the refrigerator reads 37 degrees in the refrigerator and the thermometer reads 42 degrees. I have switched the thermometers and get the same readings. Any suggestions as to what the problem is? Thank you.