You unit does not have a defrost timer.
Defrost is controlled by the control board at the back of thye unit.
I cannot find info specific to this unit. Hopefully the below unit is close to yours.
31-9215.
https://drive.google.com/drive/folde...EhtV0YxUTRrbTA
You will have to try and force a defrost cycle.
When the fans are running forcing a defrost will shut them off.
If it does not start a defrost you need to check the defrost heater and the defrost thermostat for resistance.
If both are Ok then odds are that the control board is shot.
Not6e that on some GE's the temperature sensor (thermistor) also plays a part on when a defrost will happen.
With a little luck someone else will jump in with help specific to this unit/model.