Sub-Zero Designer Code 15-1-00: Zone 1 cooling relay stuck open

What 15-1-00 means

On Sub-Zero Designer units like the DET3050CI and DEC3050R, 15-1-00 means the control-board relay that switches cooling for zone 1 reads open. Classic BI models such as the BI-36U/S and BI-48SD/S list the same code as the refrigerator relay open. In plain terms, the control asked that relay to switch cooling on, but the circuit shows it never closed. The usual sign is zone 1, or the refrigerator section on a Classic BI, slowly warming while the code sits on the display.

Common causes of 15-1-00

Relay on the control board not closing
Loose plug or open wire on the relay circuit
Control board output no longer switching

✓ One safe check you can try

1) Note the code and the model number from the tag inside the door. 2) Check zone 1 or the refrigerator side with a thermometer. 3) Move perishables if it rises above 40°F. 4) Restart the unit at the breaker once. 5) Call us promptly if the code returns.

! Why to stop there

Relay testing requires live voltage checks at the board.
Board connectors carry line voltage when the unit is on.
A replacement board must match the platform exactly.

Opening a panel yourself does not automatically cancel a manufacturer warranty, but it can cause accidental damage, and some manufacturers set their own service conditions. Check your warranty terms, or ask us, before deciding.

→Same appliance

Other Refrigerator codes

23Sub-Zero 600, 700 and 648PRO Code 23: Defrost overheat with no feedback 50Sub-Zero 600 and 700 Series Code 50: Refrigerator compressor running too long 41Sub-Zero 648PRO Code 41: Zone compressor or wiring problem 81Sub-Zero 700-2 Code 81: Variable-Speed compressor fails to start 82Sub-Zero 700-2 Code 82: VS compressor controller needs replacement 88Sub-Zero 700TF Code 88: Board and compressor controller not talking 80Sub-Zero 700TF Code 80: No inverter feedback after a board change ddSub-Zero 600 and 700 Series Display dd: Diagnostics switched off

15-1-0015-1-00 questions

What does relay open mean for 15-1-00?

The control board told its zone 1 relay to switch cooling on, but the circuit still reads open. Cooling for that section may not start, so zone 1, or the refrigerator side on a Classic BI, can warm.

Is 15-1-00 the same as 15/1/01?

No, they are opposites. 15/1/01 reports the relay stuck closed, so cooling may never switch off. 15-1-00 reports it stuck open, so cooling may not switch on when needed.

What is the repair?

We test the relay output, the board plugs and the circuit wiring, then repair the connection or replace the board after you approve a written price. Afterward we watch zone 1 cycle normally.