Frigidaire PHSC39EESS5 not going into defrost.

[tigerpilot]

Coil was frozen. Changed thermostat. Did a manual defrost. Both sides working fine. I have a recording thermometer placed in the coil compartment. The temperature has stayed within two degrees from zero for more than 30 hours. Fridge has ADC system. After the thermostat closes, what tells the system to go into a defrost cycle. It used to go about every six hours. Something isn’t working. Thinking control board in fridge section. Would like your input. Thanks, Donhttp://forum.partsdr.com/attachment.php?attachmentid=1068&d=1631627477&thumb=1

[Slav]

The ADC (Adaptive Defrost Control) should run defrost cycle anywhere from 6 hours to a maximum of 96 hours (if you don't open the door for 24 hours straight it goes into Vacation Mode).

Assuming you are opening the door often, and already changed the thermostat, the next thing would be to replace the ADC board itself.

Make sure the defrost water drains out well as well.