GE Model GSS25TGMBWW Freezer not defrosting

[HRK]

Our garage GE Fridge GSS25TGMBWW has started to not defrost properly.  Twice the unit has stopped cooling the fridge properly and the freezer is cool but not freezing cold.  Back wall has a build up of frost, in order to check if it stil operates we've empted the freezer and unplugged the unit, tossed out the ice. Upon restart it begins to cool properly, and will maintain it for about a week to two weeks then back into the non freeze mode and the back wall is covered with frost.

Indicators online are the defrost heater, defrost timer, main board...   Thinking the defrost heater would be good to start, are there tests I can perform to determine which part of the defrost cycle is the problem.  Thanks!

 

 

 

[ECtoFix]

How To Test A Defrost Heater On A Refrigerator or Freezer

How To Test Your Defrost Thermostat & How They Work

[HRK]

Thanks I"ll run both those tests, hopefully we'll find one or the other needs replacement...