Sub-Zero Designer Code 15-3-00: Zone 3 cooling relay open

What 15-3-00 means

This code is specific to current Designer models, such as the DET3050CI tall refrigerator and the DEC3050R column, where 15-3-00 means the control-board relay that switches cooling for zone 3 reads open. The control has asked for cooling in zone 3, but the relay circuit never shows a closed path. As a result, cooling for that zone may not start on demand. Most owners first notice zone 3 warming while the other zones hold their settings, along with the code on the display.

Common causes of 15-3-00

Relay on the control board not closing
Open circuit or loose plug on the zone 3 relay wiring
Control board output for zone 3 no longer switching

✓ One safe check you can try

1) Place a thermometer in zone 3 and compare it with the setting. 2) Move perishables out of zone 3 if it climbs. 3) Keep the door closed to hold the cold. 4) Restart power once at the breaker. 5) Book service promptly if 15-3-00 stays.

! Why to stop there

Relay diagnosis involves live voltage at the board.
Board connectors must be handled without bending pins.
Board replacements must be the correct Designer part.

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

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 deSub-Zero 600 and 700 Series Display de: Diagnostics enabled 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

15-3-0015-3-00 questions

Why is only zone 3 warm?

Designer units switch cooling for each zone through its own relay. Code 15-3-00 means the zone 3 relay reads open, so only that section stops getting cooling while the others carry on.

How is 15-3-00 different from 15-3-01?

15-3-00 means the relay reads open, so cooling may not start. 15-3-01 means it reads closed, so cooling may never switch off. They are opposite conditions.

What does the zone 3 relay repair involve?

We test the relay output, the board connections and the circuit wiring for zone 3, then quote the repair in writing before starting any work. After the fix we confirm zone 3 pulls down to its setting.