Sub-Zero Refrigerator Repair in Toronto — Running constantly / never shuts off

• A Sub-Zero that runs constantly is the symptom behind the EC40/EC50 over-run codes: EC40 is 'excessive freezer compressor run' and EC50 is 'excessive refrigerator compressor run,' and because this is a dual-refrigeration cabinet the code tells us which of the two sealed systems is the one that never cycles off. Sub-Zero's own EC40/EC50 tree starts at airflow, not parts: if temperatures are near setpoint we brush-and-vacuum the shared lower-grille condenser and clear the flag by holding the door-ajar alarm key 15 seconds, but if the compartment is high with the door shut and the coil clean, Sub-Zero says to stop and escalate to Factory Certified Service rather than reset a unit that will just over-run again.
• The single most preventable runs-constantly cause is a dust-blanketed condenser. Sub-Zero's care guidance is to brush/vacuum the lower-grille condenser every 3-6 months; when it cakes over, the coil can't shed heat, the compressor never reaches a satisfied cut-out, and the unit logs EC40 (freezer side) or EC50 (fridge side) with SERVICE flashing. We confirm the coil is the fault before quoting a part, because on a clean recovery the cure is maintenance plus the door-ajar-key reset, not a component.
• A condenser fan that has stalled or seized is the classic 'clean coil but still runs nonstop' Sub-Zero fault, and it is the trap on this symptom: condenser-fan failures throw NO dedicated EC code, so they surface only as EC40/EC50 over-run, never a thermistor code. The OEM condenser fan motor is 4200740 (it spans the 200 through 700 series and is serial-coded to 4200741 across a specific serial window on 430/561/601/632/642/650/680/690 units, a break we confirm by model and serial before ordering). With no airflow over the coil the compressor runs to keep up and eventually trips on thermal overload, so we direct-test the motor by hand and meter the windings rather than reading a code that isn't there.
• On the fresh-food side, a stalled evaporator/circulation fan makes the fridge-side compressor run constantly because the cold it produces never moves into the cabinet, so the control keeps calling for cooling. The OEM service motor is 7003817 (a single multi-position service part used on either the fresh-food or freezer evaporator position across 600, 700, UC-24, IC-27 and 424 units). We spin-test the blade, check winding continuity, and position-verify by model/serial before ordering, since the same number serves both sides; this is also why the EC50 fridge-side over-run can be a fan fault, not a charge problem.
• A frosted evaporator coil makes a Sub-Zero run constantly because frost insulates the coil and chokes airflow, so the system works nonstop to pull heat it can no longer reach. The defrost-system failure behind it is Sub-Zero's EC24 defrost-underheat flag; we run Sub-Zero's manual-defrost test (hold the ice-maker key to the click, energize the heaters ~15-20 min) and watch whether the coil clears. A coil that won't melt points at an open defrost heater - on 532/632-class cabinets the OEM heater is 7016048 (it supersedes to 4324690 on 632 units at/above serial #1810000) - or a stuck-open defrost terminator (7025952 on IC/IT/ID columns), and we meter continuity in defrost mode before fitting either.
• A door gasket that has lost compression keeps a Sub-Zero running constantly by letting humid room air leak in: the warm-air load never lets the compartment satisfy, and the moisture frosts the coil so airflow chokes on top of the leak. Sub-Zero's runs-constantly guidance is to run a hand along the door edge for escaping cold air and dollar-bill-test the perimeter; on 700-series units the OEM seal is model-coded (7012382 for 700TC/I-3, 700TF/I-3 and 700TR-3 at serial #3100000 and up, replacing 7010588 below that break), and gaskets are not interchangeable across the 600/700/800 series, so we confirm the exact seal by model/serial rather than fitting a near-match that keeps the unit over-running.
• When a Sub-Zero runs nonstop with a clean coil, working fans and a frost-free evaporator, the refrigerator thermistor circuit is the next stop: Sub-Zero logs EC05 ('refrigerator repeatedly read erratic temperatures' - the cabinet sensor) and EC06 (the refrigerator evaporator thermistor read open/shorted/erratic for 10+ seconds). When the board can't trust the temperature it never registers that setpoint is reached, so it drives the compressor continuously. The OEM refrigerator temperature-sensor assembly is 4204150 (fits 400/600/700 series prior to serial #2970000); we ohm the probe in ice water against spec - about 32,330 ohms at 32 F, replacing if it reads open, shorted or more than 10% out of range - and replace the sensor rather than chasing the sealed system.

Sub-Zero running constantly / never shuts off in Toronto — the local specifics

• The recurring Toronto pattern on Sub-Zero runs-constantly calls is the high-end integrated cabinet whose condenser has never been cleaned plus a custom toe-kick boxing in the lower grille - the coil cakes, airflow starves, and the unit logs EC40 or EC50 and never cycles off. The second recurring version is a stalled fan with a clean coil (no EC code at all), where the homeowner has already 'cleaned the coils' and is surprised the compressor still won't stop; we treat both as airflow-first diagnoses before touching the sealed system.
• We roll to these calls with the airflow and defrost parts that actually fix this symptom: condenser fan motor 4200740/4200741 and evaporator/circulation fan 7003817, a 7016048-class defrost heater and 7025952 terminator for a frosted-coil over-run, plus the air purification cartridge 7042798 and water filter 4204490 to refresh on the same visit - and we serial-confirm the exact 700-series gasket (7012382) or any sealed-system part through the authorized channel before the return trip.

For the full Sub-Zero refrigerator module — every fault, part number and code — see Sub-Zero refrigerator repair in Toronto, and for the same fault across all brands the refrigerator running constantly / never shuts off guide.