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Error code reference

Sub-Zero Refrigerator Error Code 15 3 01

Zone 3 compressor relay stuck closed

Sub-Zero codesSub-Zero refrigerator codes

Zone 3 compressor relay stuck closed - 120V to compressor at all times.

First step from the service manual

Verify and replace control board.

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

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What 15 3 01 means on a Sub-Zero refrigerator

Error code 15 3 01 on a Sub-Zero refrigerator indicates that the Zone 3 compressor relay has become stuck in the closed position, meaning 120 volts AC is being continuously supplied to the compressor at all times. Under normal operation, the control board cycles the compressor relay open and closed to regulate the compressor's run time based on temperature demand. When the relay welds shut or fails in the closed state, the compressor loses this controlled cycling and runs without interruption, regardless of actual cooling needs.

This condition is detected by the control board's internal monitoring circuit, which tracks relay state and voltage output. A relay stuck closed is typically caused by a failed solder joint or burned contact within the relay itself, but since the relay is integrated into or directly controlled by the control board, the board is the primary suspect. Electrical arcing across relay contacts during switching cycles is the most common root cause of contact welding, and this failure mode tends to be permanent once it occurs.

If left unresolved, continuous compressor operation can lead to overheating, compressor burnout, excessive energy consumption, and potential freezing of evaporator coils. The first and primary diagnostic step is to verify the fault condition and replace the control board, as the relay and its associated circuitry are housed within that assembly. A technician should confirm 120V is present at the compressor continuously before condemning the board, to rule out a wiring fault or short circuit elsewhere in the circuit path.

Source: manufacturer service documentation.

Common causes of 15 3 01

  1. 01

    Failed control board relay (welded contacts)

    Part replacement

    The relay on the control board that switches power to the Zone 3 compressor has welded its contacts in the closed position due to electrical arcing. This is the most likely cause and is confirmed by continuous 120V at the compressor terminals regardless of cooling demand.

  2. 02

    Defective control board

    Part replacement

    Beyond relay contact failure, broader control board failure can cause incorrect relay drive signals, leaving the relay continuously energized. Replacing the control board is the primary recommended repair step.

  3. 03

    Short circuit in compressor wiring harness

    Wiring / connection

    A short in the wiring between the control board and the compressor could mimic a stuck relay by maintaining a live voltage path. Inspect the wiring harness for chafing, pinching, or melted insulation before finalizing a diagnosis.

  4. 04

    Overheating-induced relay failure

    Part replacement

    Prolonged operation in a high-ambient-temperature environment or poor ventilation around the unit can accelerate relay contact degradation, increasing the likelihood of contact welding under load.

See the test procedure for each cause

Frequently asked questions about 15 3 01

What does 15 3 01 mean on a Sub-Zero refrigerator?
Error code 15 3 01 means the Zone 3 compressor relay is stuck in the closed position, causing 120 volts AC to be delivered to the compressor continuously rather than in controlled cycles. This is a control board relay failure. The compressor runs without stopping, which can lead to component damage if not addressed promptly.
Can I fix error code 15 3 01 myself?
The primary repair for this error is replacing the control board, which involves working with 120V AC circuits and precise component handling. Technicians with appliance electrical experience can perform this repair, but homeowners unfamiliar with line-voltage circuits should contact a qualified appliance service technician. Before replacing the board, confirming that 120V is continuously present at the compressor helps verify the diagnosis.
Is error code 15 3 01 a safety hazard?
A continuously running compressor is not an immediate safety emergency in most cases, but it does pose risks over time. Uninterrupted compressor operation can cause overheating, compressor motor burnout, and excessive wear on refrigerant system components. Addressing the fault promptly prevents the need for more extensive and costly repairs down the line.
How much does it cost to repair error code 15 3 01 on a Sub-Zero refrigerator?
Repair costs depend on whether the issue is resolved by replacing the control board or involves additional components such as wiring or the compressor itself. Control board replacement on Sub-Zero units typically falls in the range of $400 to $900 or more, including parts and labor. If the continuously running compressor has caused secondary damage, total repair costs could be higher.
Will resetting the refrigerator clear error code 15 3 01?
A power reset will not clear error code 15 3 01 if the underlying relay failure persists. Because the relay contacts are physically welded or fused closed, cycling power to the unit does not change the hardware fault state. The error will return immediately upon restart, and the compressor will continue running constantly until the control board is replaced.

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