Why is my Sub-Zero refrigerator not cooling?

Why that is usually the answer

One cabinet holding both compartments cools the two sides separately — dual refrigeration is Sub-Zero's own name for it — so a freezer still holding hard while the refrigerator has climbed says the cold is being made. Paired columns are two appliances and the shortcut does not carry across. On a side-by-side that leaves the refrigerator circuit: an evaporator fan that has quit turning, or a defrost fault packing the coil with ice because the heater or the thermistor that should clear it has failed. In Rancho Bernardo, San Diego there is a third suspect that belongs to the kitchen rather than the appliance, which is a condenser left with no clearance around its grille after a remodel. If the warmth builds through the afternoon and clears overnight, start there.

Where it usually turns out to be

The clearance version of this fault is worth describing, because it is common across this part of San Diego County and it does not present as a fault at all. A current column fitted into an opening framed for an older appliance gets its gap closed with filler strips and a trim piece, and the grille the condenser breathes through ends up passing a fraction of the air it was built for. Nothing fails. The system simply loses every bit of its margin, so it holds temperature perfectly on a cool morning and cannot keep up once the room warms, which is precisely the pattern an owner describes as intermittent. It is not intermittent. It is a unit sitting at its limit every afternoon, and the readings at the coil say so plainly.

Order of testing matters because each step rules out the one after it. The grille and the actual clearance around the cabinet come first, then the condenser and its fan, then the evaporator fan on the refrigerator side measured under load, then the defrost heater and the thermistor, because a coil packed with ice chokes off airflow before any other component gets the chance, then the seal. Sealed-system work sits at the bottom of that list deliberately. A freezer that is still hard has already told us the refrigerant side is intact, and quoting a compressor on a unit whose real problem was a trim strip is the worst wrong turn available on this equipment. Leave the unit running rather than switching it off and back on: on the newer controls a power cycle wipes the stored fault history, which is often the fastest route to the right part being on the van.

If that matches what yours is doing, say so when you call — it decides which parts come on the van.