Quick answers
- What is the sealed system on a Sub-Zero?
- The sealed system is the refrigeration loop: compressor, condenser, evaporator, filter-drier and the tubing that carries refrigerant. It's brazed closed, so opening it requires EPA-608 certification and recovery equipment. When this loop fails, both compartments drift warm even though the unit keeps running.
- How do I know if it's the compressor and not something else?
- A sealed-system fault typically shows both freezer and fridge warm with the compressor running nonstop or not at all. We confirm it with gauges on the refrigerant charge and an amp-draw reading on the compressor — that distinguishes a weak compressor, a leak, or a restriction from a fan, defrost or board fault.
- Is Sub-Zero's sealed system under warranty?
- Sub-Zero provides a 12-year manufacturer warranty on the sealed system — compressor, condenser, evaporator, drier and tubing. Coverage depends on the unit's age and proof of purchase, so verify it before paying for sealed-system parts. We can help you check whether your repair qualifies.
- Why does sealed-system repair cost more?
- Sealed-system work needs EPA-608 certification, recovery and charging equipment, and brazing, plus an evacuation and a controlled recharge. Compressor and sealed-system repairs typically run $900–$2,000, though the 12-year factory warranty on the sealed system may cover much of the parts cost.
What is the sealed system, and how does it work?
The sealed system is the heart of any Sub-Zero: a compressor pressurizes refrigerant, the condenser sheds that heat, the filter-drier and capillary meter the flow, and the evaporator absorbs heat inside the cabinet to make cold. The whole loop is brazed shut and charged with a precise amount of refrigerant. When capacity drops anywhere in that loop, both the freezer and the fresh-food side drift warm — unlike a fan, damper or defrost fault, which usually leaves one compartment cold. If only one compartment is off, you’re more likely looking at the broader Sub-Zero not-cooling causes than the sealed system.
Real causes, in order
| Symptom or sign | Likely cause | What we do |
|---|---|---|
| Both compartments warm, condenser caked with dust | Dirty condenser mimicking low capacity | Brush and vacuum the coil, then retest before any sealed-system call |
| Runs nonstop, both sides warm, coil already clean | Weak or failing compressor | Amp-draw reading on the compressor to confirm it isn’t building pressure |
| Slow, gradual warming over days or weeks | Refrigerant leak at a brazed joint or fitting | Manifold-gauge charge check, find and braze the leak, evacuate and recharge |
| Freezer fine but fridge drifts, or evaporator frosts oddly | Restricted filter-drier or capillary | Gauge readings to spot the restriction, replace the drier, recharge to plate weight |
- Dirty condenser — always ruled out first; it mimics low capacity and is the cheap fix.
- Weak or failed compressor — pulls high or low amps and no longer builds pressure.
- Refrigerant leak — a slow loss of charge that gradually warms the cabinet.
- Restricted drier or capillary — a partial blockage starves the evaporator.
Why this is gauge work
You cannot eyeball a sealed-system fault. We connect gauges to read the refrigerant charge and take an amp-draw on the compressor; together those readings tell us whether it’s a weak compressor, a leak, or a restriction. Opening the loop legally requires EPA-608 certification and recovery equipment — this is not a swap-the-part repair.
What an evacuation and recharge involves
Once a leak or restriction is confirmed and the failed component is replaced, the loop has to be pulled into a deep vacuum to boil off moisture and air, leak-checked, then charged with the exact refrigerant weight for that model from the rating plate. Get the charge or the vacuum wrong and the unit either underperforms or fails again within months — which is why this is metered, certified work rather than a quick part swap.
Why Bay Area conditions stress the sealed system
Where the refrigerator lives changes how hard that loop has to work. In the Tri-Valley and inland East Bay, summer estate kitchens sit at 90–100°F, so a condenser already loaded with dust can’t shed heat and the compressor runs long and hot — the exact load profile that finishes off a tired compressor. Wildfire-season ash packs the front grille within weeks, compounding it. Nearer the coast and the fog line, salt-laden air slowly corrodes condenser tubing and brazed joints, which is where the slow refrigerant leaks tend to start on Peninsula, Marin and San Francisco units. Many of these are built into custom estate cabinetry with stone surrounds and tight returns, so condenser airflow is already unforgiving before any of the above.
When to call, and check the warranty first
If the condenser is clean and both compartments are still warm after 24 hours, you’re likely looking at the sealed system. Before paying, confirm whether your unit is within Sub-Zero’s 12-year sealed-system warranty — it can cover the compressor and refrigeration parts. We diagnose with gauges, give a written quote backed by genuine OEM parts matched to the rating plate, and help you verify coverage before any sealed work begins. Out of warranty, see the Sub-Zero compressor replacement cost for real ranges, and the full diagnostic-first process under Sub-Zero refrigerator repair.
How we confirm it
Gauges and amp draw, not a parts guess
Refrigerant pressures on a manifold gauge set, paired with a compressor amp-draw reading, separate a tired compressor from a slow leak from a drier or capillary restriction. Those two measurements are what make a sealed-system call definitive — no other test substitutes, and no part is opened until they agree on the fault.
Rule this out first
A clogged condenser mimics a dying compressor
Before any sealed-system suspicion, the condenser gets brushed and vacuumed clean. A coil packed with dust or wildfire ash starves heat rejection and makes a healthy unit run long and warm — the exact symptom of low capacity. It is the cheap fix that saves an expensive diagnosis, so it always comes first.
Quick triage before suspecting the Sub-Zero sealed system
- Clean the condenserBrush and vacuum the condenser coils; a clogged condenser mimics low capacity and is the cheap fix to rule out first.
- Note the symptom patternCheck whether both compartments are warm and whether the compressor runs nonstop — that pattern points to the sealed system, not a fan or defrost fault.
- Wait 24 hoursGive the cabinet a full day after cleaning to recover before judging, and don't change the setpoint mid-test.
- Check warranty, then bookIf both sides stay warm, confirm whether the 12-year sealed-system warranty applies, then book a gauge-and-amp diagnostic.
How a visit works
Frequently asked questions
What is the sealed system on a Sub-Zero?
The sealed system is the refrigeration loop: compressor, condenser, evaporator, filter-drier and the tubing that carries refrigerant. It's brazed closed, so opening it requires EPA-608 certification and recovery equipment. When this loop fails, both compartments drift warm even though the unit keeps running.
How do I know if it's the compressor and not something else?
A sealed-system fault typically shows both freezer and fridge warm with the compressor running nonstop or not at all. We confirm it with gauges on the refrigerant charge and an amp-draw reading on the compressor — that distinguishes a weak compressor, a leak, or a restriction from a fan, defrost or board fault.
Is Sub-Zero's sealed system under warranty?
Sub-Zero provides a 12-year manufacturer warranty on the sealed system — compressor, condenser, evaporator, drier and tubing. Coverage depends on the unit's age and proof of purchase, so verify it before paying for sealed-system parts. We can help you check whether your repair qualifies.
Why does sealed-system repair cost more?
Sealed-system work needs EPA-608 certification, recovery and charging equipment, and brazing, plus an evacuation and a controlled recharge. Compressor and sealed-system repairs typically run $900–$2,000, though the 12-year factory warranty on the sealed system may cover much of the parts cost.
Is it worth repairing a Sub-Zero compressor?
Often yes. A well-maintained Sub-Zero runs 25–30 years, so a sealed-system repair is usually worthwhile while it costs under roughly half the price of a new built-in — and the 12-year sealed-system warranty can sharply reduce the bill. We give a written quote so you can decide.
Why is my Sub-Zero running constantly but not cold?
Constant running with both compartments warm points to the sealed system losing capacity — a tired compressor, a slow refrigerant leak, or a restriction in the drier or capillary. First rule out a dirty condenser; if cleaning it doesn't help within 24 hours, it needs a gauge-and-amp diagnostic.
What clients say
4.9 · 327 reviews
Our Sub-Zero ran nonstop yet both compartments stayed warm. The tech connected manifold gauges and took a compressor amp-draw reading that confirmed a slow refrigerant leak at a corroded brazed joint, not a dead compressor. EPA-608 recovery, repair, deep vacuum and a weighed-in recharge. It's held perfectly since.
Both fridge and freezer warm, so I expected the worst. He insisted on cleaning the dust-choked condenser first and gave it 24 hours before any sealed-system talk. When it still ran warm, gauges confirmed a restricted filter-drier. He checked our 12-year warranty before quoting a dollar.
Salt air near the bay had corroded the condenser tubing on our built-in and the sealed system lost charge. The technician explained it couldn't be eyeballed, did the gauge-and-amp diagnostic, replaced the leaking section and recharged to the rating-plate weight. Took two visits for parts but the work was meticulous.