Sub-Zero EC24 - "Defrost Underheat"
What this means- EC24 is a code related to your defrost system. It is triggered when your sub zero computer has sensed that a defrost cycle has run longer than it is supposed to. This means that there is a high probability your evaporator coil is frozen over or experiencing a defrost issue or airflow issue.
Watch this video to see a defrost issue on a 600 series:
What to do: The very first thing I would do is check your defrost heaters. Most sub zero units have a manual defrost mode. On the 600 and 700 series, you will hold your ice maker button down until you hear a distinctive click! This will tell the control board to shut off your freezer compressor and turn on your defrost heaters. After a few minutes you should hear your heaters hissing away in the freezer while they melt excess frost build up.
How to enter defrost mode:
Do you hear your heaters working? Let them run a full heat cycle and see how much frost has been melted. This should be about 15 to 20 minutes. If it melts all the frost your heaters are probably good! If you know how use an ohm meter, check them for continuity.
Hear nothing melting? Check to see if you are getting voltage to your heaters, perhaps the "defrost terminator switch" is stuck open and not allowing voltage to reach your heaters. In this situation, a simple voltage read at the terminator switch should be confirmed 120v, and if we have that voltage we can then see if the heaters are getting 120v. If your terminator receives 120v and your heaters do not, you most likely have a bad terminator switch, which is common.
If your heaters and terminator switch are both good you need to check your fans and your airflow.
Why Airflow? - Airflow keeps your coil from frosting up, if we are creating too much frost, the defrosters can melt it all, check your fan! If your fan is still spinning and not impeded, you probably an issue correlated with your defrost system itself. However it is important to do a test where you close the door completely and make sure that all switches that control your fans and lights are being hit. Sometimes well put our iPhone on video mode and put it in the freezer. the video should reveal the door closes and hits all switches as the lights go out and fan begins to spin.
Check This Video - We found an irregular sounding fan, this was undoubtably the issues with this unit.