mypros+
Error code reference

Sub-Zero Refrigerator Error Code 20 2 50

Defrost heater open circuit detected.

Sub-Zero codesSub-Zero refrigerator codes

Defrost heater open circuit detected.

First step from the service manual

Verify wiring and heater. Check heater ohms. Replace heater if necessary.

The complete diagnostic procedure includes additional test steps, resistance specifications, wiring diagram references, and component test points.

MyPros+ Max

Get the full diagnostic procedure for 20 2 50.

  • Step-by-step tests with expected resistance, voltage, and continuity values
  • Wiring diagram references and connector pinouts from the OEM service manual
  • Verified part numbers when replacement is required
Get the full procedure

$29/month · Cancel anytime · Or $9.95 3-day pass

What 20 2 50 means on a Sub-Zero refrigerator

Error code 20 2 50 on a Sub-Zero refrigerator indicates that the control system has detected an open circuit in the defrost heater. The defrost heater is a critical component in the automatic defrost cycle, responsible for melting frost and ice buildup off the evaporator coils at scheduled intervals. When the controller attempts to energize the defrost heater and detects no continuity through the circuit, it logs this fault code to alert technicians that the defrost system cannot complete its cycle.

An open circuit in the defrost heater typically means either the heater element itself has failed internally, or there is a break somewhere in the wiring harness connecting the heater to the control board. The heater element can burn out over time due to repeated thermal cycling, causing the resistance wire inside to fracture and break continuity. The first diagnostic step is to verify all wiring connections are secure and undamaged, then measure the heater's resistance with a multimeter. A functional defrost heater will show a measurable ohm reading; an open circuit will read OL or infinite resistance, confirming the element has failed.

If the wiring checks out and the heater itself reads open, the heater must be replaced to restore normal defrost operation. Leaving this fault unaddressed will cause progressive frost accumulation on the evaporator coils, eventually restricting airflow and leading to cooling performance degradation throughout the refrigerator and freezer compartments.

Source: manufacturer service documentation.

Common causes of 20 2 50

  1. 01

    Failed defrost heater element

    Part replacement

    The heater element itself has developed an internal break, resulting in an open circuit. Confirm by measuring resistance across the heater terminals with a multimeter; an OL or infinite reading confirms the element is burned out and must be replaced.

  2. 02

    Broken or damaged wiring harness

    Wiring / connection

    A wire in the circuit between the defrost heater and the control board may have cracked, corroded, or come loose at a connector. Visually inspect all wiring and connectors in the defrost heater circuit for signs of damage, corrosion, or disconnection before condemning the heater itself.

  3. 03

    Loose or corroded connector terminals

    Wiring / connection

    Connector terminals at the heater plug or at the control board can loosen or corrode over time, interrupting continuity even if the heater element is intact. Inspect all plugs in the defrost heater circuit and reseat or clean any suspect connections.

  4. 04

    Thermal limiter or thermal fuse failure

    Part replacement

    Some defrost heater circuits include a thermal cutout device in series with the heater. If this limiter trips or fails open, it will produce the same open circuit fault as a failed heater element. Check for any in-line thermal devices in the heater circuit and test them for continuity.

See the test procedure for each cause

Frequently asked questions about 20 2 50

What does 20 2 50 mean on a Sub-Zero refrigerator?
Error code 20 2 50 means the refrigerator's control system has detected an open circuit in the defrost heater. This indicates no continuity exists in the defrost heater circuit, which prevents the unit from completing its automatic defrost cycle. The cause is typically a burned-out heater element or a broken wire in the heater circuit. A technician will need to test the heater resistance and inspect the wiring to confirm the fault.
Can I fix error code 20 2 50 myself?
A knowledgeable DIYer can perform the initial diagnostics, which involve inspecting wiring connections and measuring heater resistance with a multimeter. If the heater element tests open, replacing it requires disassembling the freezer interior to access the evaporator coils, which is a moderately involved repair. Because the work involves working around refrigeration components and electrical circuits, many owners choose to have a certified technician handle the replacement.
Is it safe to keep using my Sub-Zero refrigerator with error code 20 2 50?
The refrigerator will continue to run in the short term, but without a functioning defrost heater, frost will accumulate on the evaporator coils over time. This buildup progressively restricts airflow and will cause the unit to lose cooling efficiency, potentially allowing food to reach unsafe temperatures. It is best to have the fault diagnosed and repaired promptly rather than continuing to use the unit in this condition.
How much does it cost to repair error code 20 2 50 on a Sub-Zero refrigerator?
Repair costs vary depending on whether only the heater element needs replacement or if wiring repairs are also required. Parts and labor for a defrost heater replacement on a Sub-Zero unit typically range from around $150 to $400 or more, reflecting both the cost of genuine replacement parts and the labor involved in accessing the evaporator assembly. Getting a diagnostic estimate from an authorized service provider before authorizing repairs is recommended.
Will resetting my Sub-Zero refrigerator clear error code 20 2 50?
Resetting the unit may temporarily clear the fault display, but the error will return as soon as the control system runs the defrost cycle again and detects the open circuit. Because the underlying cause is a physical failure of the heater element or wiring, the fault cannot be permanently resolved without repairing or replacing the defective component. A reset should only be used as part of the diagnostic process, not as a substitute for the actual repair.

Related Sub-Zero refrigerator codes

All Sub-Zero refrigerator codes
View all 296 Sub-Zero refrigerator codes

78,000+ service manuals · 160,000+ error codes · 55+ brands

Get Started

$29/month · Cancel anytime · Or $9.95 3-day pass