Frost or ice buildup in a Sub-Zero is caused by a failed defrost heater, defrost sensor or control (so the evaporator never defrosts), or by warm, humid air entering through a torn gasket, a misaligned door or a door left ajar.
Frost inside a frost-free Sub-Zero is a symptom, not a normal condition. It's either a defrost failure or humid air getting in.
Never chip ice with a knife, screwdriver or ice pick. Punctured evaporators are one of the most common avoidable sealed system repairs.
Check These First (5 Minutes, No Tools)
- Inspect gaskets for tears, flat spots or gaps.
- Make sure doors close on their own from halfway open.
- Check that nothing prevents the door or drawer from closing.
- Note where the frost is: a uniformly frosted back wall points to defrost; frost near the door points to the seal.
Most Common Causes
| Cause | What happens | Fix |
|---|---|---|
| Defrost heater | Open heater element; no defrost. | Pro |
| Defrost sensor / thermistor | Defrost ends too early or never starts. | Pro |
| Control board | Defrost cycle never initiated. | Pro |
| Gasket | Humid air enters continuously. | DIY / Pro |
| Door hinge / closer | Door doesn't fully close. | Pro |
How We Fix It
We test the defrost heater, sensor and control, inspect the seal and door alignment, and clear the drain. A manual defrost alone only buys a few days.
When to Call a Technician
If the basic checks above don't solve it within a few hours, or if you hear repeated clicking, see an alarm or service indicator, or notice water under cabinetry, call us at (725) 237-7399. The $75 service call is credited toward your repair, repairs carry a 1-year parts and 180-day labor warranty, and we stock the Sub-Zero parts behind most of these failures.
Typical Cost
| Repair | Typical range |
|---|---|
| Defrost heater / defrost sensor repair | $395 – $745 |
| Door or drawer gasket replacement | $295 – $595 |
| Hinge / door closer repair & alignment | $295 – $595 |
Typical totals for parts and labor in the Las Vegas area. The $75 service call is credited toward your repair, and every repair is backed by a 1-year parts and 180-day labor warranty. Your exact price depends on the model, the part and access, and you approve a firm quote before any work begins. Full price list →
Still Not Working? We Can Help Today.
$75 service call, credited toward your repair · 1-year parts · 180-day labor warranty · EPA 608 certified · Mon–Fri 8am–7pm · Sat–Sun 8am–4pm