Sub-Zero Repair Redmond · WA (425) 905-2822

Seen on: 600 Series, later control

EC 21: Defrost Overheat

EC 21 is stored when a later 600 Series freezer defrost overheats. Sub-Zero's list points at a sensor or heater that has shifted on the coil, a heater wire on the wrong board terminal or shorted, and a terminator that will not cut out. Sub-Zero Repair Redmond works through it; call (425) 905-2822.

EC 21 at a glance — Sub-Zero Repair Redmond, (425) 905-2822
Means The freezer coil ran hotter during defrost than the control permits, the opposite of the under-heat codes.
Check first
  • Whether the freezer holds its set temperature between defrosts, going by the display.
  • Whether EC 40 is stored as well; the manual clears up EC 21 before it.
Needs a technician
  • Freezer evaporator sensor and defrost heater checked for correct mounting and position, and remounted if they have moved.
  • The heater feed wire confirmed on the right board terminal and not shorted to another circuit.
  • Defrost terminator tested against its cut-in and cut-out temperatures and replaced if it misbehaves.

Where the heat is meant to stop

In a defrost, a heater warms the freezer coil and a terminator switch cuts the heat once the coil is clear. EC 21 is the control reporting that the coil got warmer than it should have before the heat stopped.

Why position comes first

The first step on Sub-Zero’s list is the mounting of the evaporator sensor and the heater. If either has shifted from its place on the coil, the reading and the heat no longer line up, and the control can judge the defrost wrongly.

The same table has EC 23 for an overheat that also lacked feedback at the start of defrost. EC 21 carries no feedback complaint, which keeps the search on mounting, the heater wire and the terminator.

Multimeter probes on an exposed control board and wiring harness in the machine compartment under a stainless unit

Asked on the phone

What temperature should the defrost stop at?
Sub-Zero rates the 600-3 defrost terminator to cut out at 55°F and cut back in at 30°F. The 601F-3 is the exception, cutting out at 70°F. A terminator that stays closed past that is one cause of EC 21. Sub-Zero Repair Redmond, (425) 905-2822, tests it.

EC 21 on your display?

(425) 905-2822 Book a visit

Sub-Zero Repair Redmond · $89 service call, deducted once the repair goes ahead · on site 0800 to 2000 hrs, all seven days

Checked by
Dean Halvorsen
Bench
sealed systems and airflow
Trade
19 yrs
Card
EPA 608 certified
Revised
Overhead view of an open machine compartment with bagged relays, a multimeter and screwdrivers on the carpet beside it

Next step

Series, readout,
then a price

Give us the model off the tag and whatever the display is showing. When the fix is a clean condenser or a reset you can do yourself, you will hear that on the phone. When it needs a technician, the visit is $89 and it comes off the repair bill; the price for the work is in writing before anything is opened.

(425) 905-2822 Book a visit

Sub-Zero Repair Redmond · on site 0800 to 2000 hrs, all seven days · calls taken 24/7