The first thing you should do is determine which one is faulty.
Start with the defrost timer that is located in the control panel in the fridge section.
With the compressor running turn the knob of the defrost timer until the compressor shut off.
Look in the freezer section and see if the heater is on and melting the ice.
If the ice is melting you will know that the heater and defrost thermostat are good and don't need to be replaced.
The defrost cycle lasts about 20 to 25 minutes.
If the fridge does not start back up you will have to turn the knob on the timer again to start the compressor.
Here is a link to your fridge model TPH21PBSMWW.
Here is the defrost timer.  |