Quick answers
- Why is my Sub-Zero freezer not freezing but the fridge is still cold?
- Because the fault is on the freezer's own cooling side. The most common cause is a defrost failure that lets frost blanket the evaporator, so it can no longer pull the freezer down to 0°F even though a little residual cold still keeps the fridge cool. A failed evaporator fan or a drawer that no longer seals does the same thing.
- What temperature should a Sub-Zero freezer hold?
- 0°F is the target, and a healthy unit holds it within a degree or two. If your freezer drifts into the teens or twenties while the fresh-food side reads a normal 38°F, that split is the diagnostic clue — it tells us to look at the freezer evaporator and defrost system, not the damper or the fridge airflow.
- My ice cream is soft but everything else seems frozen — is that a problem?
- Yes, it is the earliest warning. Ice cream loses its firmness around 10°F, so soft ice cream while the rest still feels frozen means the freezer is running warmer than it should and is on its way to a real failure. Log the temperature for a day and book before the contents thaw.
- Could a frosted-up freezer be why it stopped freezing?
- Frequently. When the automatic defrost cycle fails — a bad heater, a drifted thermistor or bimetal, or a clogged drain — frost builds on the evaporator coil and insulates it. The coil can no longer absorb heat, so the freezer slowly warms. You may see a thick white slab on the back wall behind the drawers.
How to check a Sub-Zero freezer that isn't freezing
- Put a thermometer in the freezerSet a thermometer between packages and read it morning and night for 24 hours. A drift into the teens or higher while the fridge holds near 38°F confirms a freezer-side fault.
- Inspect the seal and the drawerRun the dollar-bill test on the gasket and make sure no package or ice ridge is holding a bottom-freezer drawer open on its runner.
- Look for a frost slabEmpty the drawers and check the back wall. A thick coat of frost on the evaporator points to a defrost-system failure rather than a seal.
- Log it and bookRecord the readings and what you saw. If the freezer stays warm after the door and drawer seal properly, it needs a diagnostic — book one with your model number ready.
A warm freezer is a different problem than a warm fridge
It is worth being precise, because the two symptoms send a technician to opposite ends of the appliance. When the fresh-food side is warm but the freezer is cold, the cold is being made fine and simply isn’t being delivered upstairs — that is an airflow, damper or fan problem, and our Sub-Zero not cooling page walks through it. This page is the reverse: the freezer itself is warm, which means the cold-making side is the one in trouble. The fridge can stay deceptively cold for a while because a little residual cold still spills into it, which is why so many people blame the freezer last and lose a tub of ice cream before they act.
What stops a Sub-Zero freezer from freezing, in order
Most freezer-not-freezing calls come down to four causes, and they sort roughly by how often we see them:
- Defrost failure (frost-blanketed evaporator). Every Sub-Zero runs an automatic defrost cycle to keep the evaporator clear. When the defrost heater, the thermistor or bimetal terminator, or the control fails, frost builds into a thick slab that insulates the coil so it can no longer absorb heat. The freezer warms slowly even though the compressor keeps running.
- Drawer or door seal. Bottom-freezer drawers and freezer columns lose their seal at the gasket first. A hardened gasket, or a frost ridge that holds a drawer a few millimeters open on its runner, lets warm room air leak in faster than the unit can remove it.
- Evaporator fan. If the fan that pushes air across the freezer evaporator slows or stalls, the cold stays trapped at the coil and the cabinet warms. This often arrives with a chirp or grind you can hear from inside the freezer.
- Sealed-system fault. Least common, but a refrigerant or compressor problem starves the evaporator of its cooling capacity. This is the costliest outcome, and the reason an honest diagnostic matters before anyone quotes a compressor.
Symptom to likely cause
| What you notice | Likely cause | What we do |
|---|---|---|
| Soft ice cream, fridge still cold | Early freezer warming — log it now | 24-hour temperature log, then targeted diagnosis |
| Thick frost slab on the back wall | Defrost heater, thermistor or control | Read the frost, replace the failed defrost part |
| Drawer won’t pull fully shut | Frost ridge or hardened gasket | Clear the runner, replace the drawer seal |
| Chirp or grind plus warming | Stalled evaporator fan | Test and replace the OEM fan motor |
| Both sides slowly warm, runs nonstop | Sealed-system or compressor | Sealed-system diagnostic before any quote |
A 24-hour freezer log is the single most useful thing you can hand us — our temperature-log diagnostic page explains exactly how to take one, and if a code is showing, cross-check it against the Sub-Zero error codes list.
Why this turns up in Tri-Valley built-ins
The freezer faults we see most around San Ramon track the local conditions. Hard water through Dougherty Valley and Windemere scales the defrost drain and the ice circuit, so frost faults and clogged drains show up earlier than they would on softer water. The tall column and bottom-drawer freezers fitted into Blackhawk, Canyon Lakes and Diablo-area estate kitchens carry custom panels and heavy drawers, and it is the gasket that wears first as humid air works at the seal. And an inland condenser caked with summer dust quietly costs the whole system capacity, so a freezer that was coping suddenly can’t. We work by appointment with white-glove access for gated and hillside homes, carry genuine OEM defrost parts, fan motors and drawer gaskets matched to your rating plate, and fix the fault in one visit where we can. Most non-sealed freezer repairs land in the mid band on our San Ramon repair cost page; the flat $89 service call is waived with any repair.
Frequently asked questions
Why is my Sub-Zero freezer not freezing but the fridge is still cold?
Because the fault is on the freezer's own cooling side. The most common cause is a defrost failure that lets frost blanket the evaporator, so it can no longer pull the freezer down to 0°F even though a little residual cold still keeps the fridge cool. A failed evaporator fan or a drawer that no longer seals does the same thing.
What temperature should a Sub-Zero freezer hold?
0°F is the target, and a healthy unit holds it within a degree or two. If your freezer drifts into the teens or twenties while the fresh-food side reads a normal 38°F, that split is the diagnostic clue — it tells us to look at the freezer evaporator and defrost system, not the damper or the fridge airflow.
My ice cream is soft but everything else seems frozen — is that a problem?
Yes, it is the earliest warning. Ice cream loses its firmness around 10°F, so soft ice cream while the rest still feels frozen means the freezer is running warmer than it should and is on its way to a real failure. Log the temperature for a day and book before the contents thaw.
Could a frosted-up freezer be why it stopped freezing?
Frequently. When the automatic defrost cycle fails — a bad heater, a drifted thermistor or bimetal, or a clogged drain — frost builds on the evaporator coil and insulates it. The coil can no longer absorb heat, so the freezer slowly warms. You may see a thick white slab on the back wall behind the drawers.
Why does this happen to built-in freezers around San Ramon?
Hard water across Dougherty Valley and Windemere scales the defrost drain and ice circuit, accelerating frost faults, and the tall column and drawer freezers in Tri-Valley estate kitchens wear their door and drawer gaskets where humid air sneaks in. Inland heat on a dusty condenser quietly drags down the whole system's capacity.
What clients say
4.9 · 327 reviews
Our ice cream went soft but the fridge was perfectly cold, so I almost ignored it. Glad I logged the freezer — it was creeping into the high teens. The tech found a failed defrost heater letting frost blanket the evaporator, fitted an OEM heater and thermistor, and the freezer was back at zero by the next morning.
Bottom freezer drawer on our built-in stopped freezing properly. He showed me the gasket had hardened and a frost ridge was holding the drawer a few millimeters open every cycle. Replaced the seal, cleared the ice off the runner, and explained the hard-water angle on our defrost drain. Holds a solid zero now.
Freezer column drifting warm while the fridge side stayed fine. I sent a 24-hour log ahead of the visit, which pointed straight at the evaporator. Turned out to be a tired evaporator fan plus a partly clogged defrost drain. Both fixed in one careful visit around our panels, written quote held.