A Sub-Zero refrigerator that’s stopped holding temperature is unsettling, but the cause is usually one of a short list of specific, diagnosable parts — not the whole cooling system failing at once.
Start With the Door Seal
A door seal that’s lost its compression is one of the most common causes of a fridge running warm, since it lets a steady trickle of warm air in even when the door looks closed. Run a dollar-bill test: close it in the door and pull gently — if it slides out easily, the seal has lost its grip.
Check for an Excessive-Runtime Problem
If the compressor seems to run constantly without cycling off, that’s often reported directly as error code 40/1/40 on Classic Built-In Series units.
Rule Out a Sensor Problem
If the seal is fine and the compressor cycles normally but the compartment still won’t hold temperature, a drifting or failed sensor is the next most likely cause.
Getting It Fixed
Treat a warm refrigerator as same-day — most units hold safe temperature for a few hours after a real problem, but that window closes fast. Visit our refrigerator repair page to book a visit.