EC 24 is a defrost under-heat: the control started a defrost cycle on the freezer coil and did not see the coil reach the temperature that cycle is supposed to produce.
- What the control is watching
- The freezer evaporator during a defrost cycle — whether the coil actually warms up once the heater has been called for.
- What makes it register
- A defrost that finishes with the coil still cold. The heater circuit is reporting normally; the heat is not arriving.
- Can you keep using it
- For a day or two, yes, though the freezer will frost over progressively and the compartment will start losing ground. It does not fix itself.
Nothing about this code points at the compressor, and that is the useful part of it. The cold is being made; it is the twice-daily thaw that is failing, so ice accumulates on the coil until air can no longer pass through it. The compartment then gets warmer while the machine works harder, which is why the complaint that arrives is usually about temperature rather than about frost.
The order of testing follows the manufacturer’s own: heater resistance first, then whether the heater and the freezer evaporator thermistor are mounted where they belong, then the wiring between them and the control. Each step rules out a part rather than assuming one, which matters here because the three answers cost very different amounts.
Clearing the ice by hand will restore the freezer for a fortnight and change nothing. The code is worth acting on while it is still only a defrost fault.
What we usually find
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Ice rebuilding across the back wall within days of somebody clearing it, and this code on the panel
The defrost heater itself, open circuit. It is the commonest single answer to this code and it is the first thing measured.
Defrost heater, thermostat or sensor $280–$640
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A coil that partly clears — bare at the top, solid at the bottom
A heater still working but not sitting where it should, or an evaporator thermistor that has been remounted out of position, so the heat and the sensor are in different places.
Defrost heater, thermostat or sensor $280–$640
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The code returning a week after a heater was already replaced
Connections rather than components — a terminal that looked fine cold and opens up warm. Worth ruling out before anybody talks about a board, which is why no band is put against it here.
Quoted after the diagnosis
Which of these it is gets settled at the visit, before a part is ordered — Sub-Zero Repair Pro Los Angeles, (310) 844-1973.
- Written by
- Yuki Tanabe
- Role
- Refrigeration technician — controls and sensors
- In the trade
- 18 years in the trade
