Sub-Zero Error Code 15 1 00: Refrigerator Compressor Relay Stuck Open

Sub-Zero code 15 1 00 on a Built-In (BI) unit indicates the refrigerator compressor relay is stuck open, meaning the control board cannot deliver power to the compressor. Because the compressor is the heart of the cooling system, a stuck-open relay typically results in a warming refrigerator section. The fault points to the relay on the control board, so verification and, in most cases, a control-board replacement are required.

This is not a do-it-yourself repair. The relay is part of a board that switches high-voltage loads, and the compressor circuit must be diagnosed by a qualified technician. Treat any rising refrigerator temperature as urgent for food safety.

What 15 1 00 indicates

The control board uses a relay to switch line power to the compressor. "Stuck open" means the relay contacts are not closing, so the compressor never receives power and cannot run. Sub-Zero's guidance is to verify the condition and, if confirmed, replace the control board, since the relay is integrated into the board and is not serviced separately. The diagnosis must confirm that the relay, not the compressor itself or its wiring, is the failure point.

Likely causes

• Failed compressor relay on the control board (contacts not closing)
• Damaged or degraded control board from age, heat, or a power surge
• Corrosion or solder-joint failure on the board's relay circuit
• Upstream power or wiring fault preventing the relay from energizing
• Compressor start components masking or contributing to the no-start condition (must be verified)

Owner-safe checks for 15 1 00

• Check that the unit has power and the household breaker for the refrigerator has not tripped.
• Power cycle the unit at the breaker for about 5 minutes, then restore power to see if the relay re-engages.
• Move perishable food to another refrigerator if the fresh-food section is warming.
• Listen for whether the compressor attempts to start; report what you hear to the technician.

When to call a technician

Confirming a stuck-open relay means testing for power at the compressor under board control and verifying the compressor and start components are healthy before condemning the board. This involves live high-voltage measurements and access to the control board, which is hazardous and requires a qualified technician. In most cases the corrective action is a control-board replacement, which should only follow proper verification.