Replace the defrost sensor if it shows no continuity at around 0 degrees f.
Auto defrost freezer not working.
Move on to the next step if this does not resolve the defrosting issue.
5 check if the defrost timer defrost heater and the thermostat are working correctly.
If the defrost sensor trips because it s not working correctly frost builds up on the evaporator fins eventually making the refrigerator and freezer not cool well.
You can use volt ohm meter to check the defrost sensor for continuity.
The automatic defrost should now work if there is no other issues with the defrost system.
If any of them fails to function the defrost system will not function.
If the defrost timer is not advancing replace it.
It requires the owner to manually defrost the freezer coils as frost builds up.
A quick fix if the fridge freezer is working ok but the auto defrost is not is to connect it to the mains via a 24hr timer.
All you have to do is set it to come on for 15mins then of for 30 mins.
A defrost thermostat opens the heater circuit when the evaporator temperature rises above a preset temperature 40 f 5 c or more thereby preventing excessive heating of the freezer compartment.
A manual defrost freezer does not contain any automatic heating elements to prevent the build up of frost or ice.
When the coils are covered by too much frost and ice airflow is restricted and the freezer won t efficiently cool food.
If the defrost heater assembly is defective the defrost system will not work and frost will continue to accumulate.