DIAGNOSTICS
Error codes & common symptoms
The same code can mean different things across Sub-Zero generations. Tell us your exact model and what the panel shows — that's enough for us to know what to bring.
Most common — no code needed
Most calls start with a symptom, not a code. These cover what we hear most often.
Not cooling / warm / running all the time
Checked in order
dirty condenser → blocked ventilation → door not sealing → fan → thermistor → sealed system/compressor
Condenser cleaning recommended every 6–12 months on modern undercounter units.
Water inside refrigerator / water under crisper
Checked in order
clogged or frozen drain tube
Very common on older 200/300/500/600 Series.
Ice on back wall
Checked in order
drain frozen/clogged → defrost cycle → airflow → door sealing / moisture infiltration
Ice maker not making ice
Checked in order
ice maker ON → freezer temperature → water supply → water pressure → filter → frozen fill tube → water valve → stuck cube / jammed ejector
Flashing ice cube icon
Checked in order
water valve energized too long → pressure → valve → fill problems
Standalone ice maker — no ice
Checked in order
water/filter/pressure → dirty condenser → high ambient temperature → delay mode → drain → power → water supply
Ice machine — water standing inside
Checked in order
kinked drain → incorrect drain routing → drain obstruction → cleaning/sanitizing
Error code reference
EC05
600/700 Series and relatedRefrigerator Thermistor Fault
Refrigerator cabinet thermistor open/shorted, or erratic temperature reading.
Checked in order
thermistor → wiring/connections → control board input
EC06
600/700 Series, Wine unitsEvaporator Thermistor Fault
Evaporator thermistor open/shorted or erratic reading. On wine units, refers to the thermistor of the specific cooling zone — model matters.
Checked in order
thermistor → harness/connectors → resistance/readings → board input
EC20
600 SeriesDefrost Underheat
Defrost cycle started but expected heat/voltage feedback wasn't seen.
Checked in order
defrost heater → terminator → wiring → relay/control board
EC21
600 SeriesDefrost Overheat
Temperature during defrost exceeded allowed threshold — possible termination sensor or control circuit issue.
Checked in order
defrost termination sensor → control circuit
EC24
600 SeriesDefrost Underheat
Defrost cycle problem, same family as EC20.
Checked in order
defrost heater → terminator → wiring
EC40
600, 648PRO, 700 SeriesExcessive Freezer Compressor Run
Freezer compressor running too long. Check condenser first before assuming compressor failure.
Checked in order
condenser cleanliness → door seal / left open → evaporator fan → thermistor → airflow → sealed system / refrigerant → compressor
EC50
600/700 Series, DesignerExcessive Refrigerator Compressor Run
Same as EC40 but for refrigerator side/zone. On Designer, check kickplate ventilation too.
Checked in order
condenser → airflow → door seal → fan → thermistor → sealed system
EE
UC Undercounter SeriesThermistor Fault
Thermistor failure — display position indicates whether refrigerator or freezer sensor.
Checked in order
thermistor location on display → thermistor → wiring
30 8 05
BI SeriesIce Maker / Water Fill Fault
Control isn't getting a normal signal from the ice maker during fill/cycle.
Checked in order
ice maker enabled → freezer temperature → stuck cube → ice maker mechanism → water valve/fill circuit
30
736 SeriesIce Maker Water Valve Timeout
System disabled ice maker after abnormally long water-valve solenoid activation — often a stuck cube.
Checked in order
stuck ice cube → harvest cycle → water valve solenoid
50 U 86
Classic Built-In SeriesLow / Slow Water Flow
Flow meter detects water but flow rate is too low.
Checked in order
water pressure → filter → supply line → kink/restriction → valve → flow meter
50 U 87
Classic Built-In SeriesNo Water Flow
Water flow meter sees no flow at all — especially relevant for dispenser/water systems.
Checked in order
water supply → flow meter → valve
15 1 00
Classic Built-In SeriesRefrigerator Relay Open
Relay error family — exact meaning depends on model family.
Checked in order
relay → control board
15 2 01
Classic Built-In SeriesFreezer Compressor Relay Stuck Closed
Relay error family.
Checked in order
relay → control board
40 1 40
Designer Integrated SeriesExcessive Runtime, Zone 1
Cooling/runtime performance fault for Zone 1.
Checked in order
condenser → airflow → door seal → sealed system
40 3 40
Designer Wine StorageExcessive Runtime, Zone 3 (Wine)
Cooling/runtime performance fault for wine storage zone.
Checked in order
condenser → airflow → sealed system
Read us the exact code from the panel
Model, serial, and the exact code get the right technician and parts on the first visit.
(773) 448-4401