Sub-Zero Designer Code 10-3-10: Zone 3 coil sensor open

What 10-3-10 means

On Designer units including the DET3050CI and DEC3050R, 10-3-10 means the zone 3 evaporator thermistor reads open, so the control has no coil temperature for that zone. Classic BI models like the BI-36U/S and BI-48SD/S list this code as condenser sensor open. On Designer units the evaporator reading guides defrost, so an open sensor can let frost build on the zone 3 coil and reduce cooling over several days. On the Classic BI the control loses its condenser temperature input.

Common causes of 10-3-10

Open evaporator thermistor in zone 3 (Designer) or open condenser sensor (Classic BI)
Wire break between the sensor and the control
Connector separated near the coil or condenser

✓ One safe check you can try

1) Note the full code and your model number. 2) On a Designer unit, look for thick frost on the zone 3 back panel. 3) Do not chip ice or use heat inside the cabinet. 4) Restart at the breaker once. 5) Schedule a visit if the code persists.

! Why to stop there

Evaporator sensors sit behind covers that may be iced over.
An open circuit must be traced to find where it breaks.
Sensor position on the coil affects defrost accuracy.

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.

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10-3-1010-3-10 questions

What does an open evaporator sensor do to zone 3?

The control cannot read the coil temperature, so it may not defrost correctly. Frost can then build on the zone 3 coil and slowly reduce airflow and cooling.

Does a Classic BI read 10-3-10 the same way?

No. On Classic BI units this code is listed as the condenser sensor reading open, which concerns the machine compartment rather than a coil inside the cabinet.

How is it repaired?

We thaw the coil if necessary, test the sensor and wiring, and replace or repair as needed. Before any of that starts, you see the cost on paper and decide whether to go ahead.