I have a whirlpool refridgerator #GD5RHAXNQ00. It is not cooling like it used to. I removed the back panel in the freezer and the finned coil
was covered in ice. I checked the heating coil for continuity and its ok.
Is there a sensor that controls the defrost or is it done by way of that
circuit board in the white box at the bottom of the refridgerator.
My Beer is not as cold as it should be!
Usually it is timed interval, such as 30 minutes of the heating element every 24 hours. Look for a little round stud about the diameter of a pencil that you can turn using a large screwdriver. Usually it is on the top panel of the refrigerator compartment towards the back, but sometimes it could be outside on the back and you have to pull the fridge away from the wall. Sometimes turning the stud frees up the timer if it got stuck but you need to keep an eye on it and be prepared to replace it. Sometimes you can hear the refrigerator go into the defrost interval by the sound of a fan and stopping of the compressor, as you turn the stud, otherwise it is trial and error to activate the defrost interval manually.
The good conscientious technician or serviceperson will carry extra oils and lubricants in case the new pump did not come with oil or the oil was accidentally spilled, so the service call can be completed without an extra visit.