Expert: Dennis replied:
Hello,
Sub-Zero Error code: EC21 EC24
Cause of error code: Defrost Functionality Issue
Solution 1: If temperatures are high call for service.
Solution 2: If temperatures are near normal range:
a – Clean the condenser
b – Press and hold the door ajar alarm key for 15 seconds to clear the error code
c – If EC Service light appears, or temperatures rise contact service for repair: 800-440-8583
Defrost overheats means the defrost temperature exceeded the temperature where the heater should have stopped already. This is a problem with the defrost termination thermostat. This part should have open up the heater circuit already once the temperature of the evaporator is above freezing temperature.