Sub-Zero Classic BI Code 90-R-38: Refrigerator evaporator fan output error

What 90-R-38 means

Classic Built-In units like the BI-36U/S and BI-36UFD/S display 90-R-38 when the FET power output on the control board for the refrigerator evaporator fan has failed. That fan moves cold air from the refrigerator coil into the fresh-food section. When it stops, the fresh-food side warms and humidity may rise, while the freezer, cooled separately, may still hold temperature for some time.

Common causes of 90-R-38

Failed refrigerator evaporator fan output on the board
Shorted or seized refrigerator evaporator fan
Wiring damage on the refrigerator fan circuit

✓ One safe check you can try

1. Note 90-R-38. 2. Open the fresh-food door briefly and listen for the fan. 3. Move items away from the back vents. 4. Try a single breaker reset of about two minutes. 5. Watch the temperature and call us if it rises above 40°F.

! Why to stop there

The fan is behind the refrigerator evaporator cover.
A shorted fan can damage a replacement board.
Testing needs power on and live wiring access.

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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Other Refrigerator codes

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 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

90-R-3890-R-38 questions

Why is my fresh-food section warm?

The refrigerator evaporator fan moves cold air off the coil into that section. 90-R-38 means its board output failed, so cold air is not circulating even though the coil itself may be frosty.

Can I keep the food inside?

Check with a thermometer. If it rises above 40°F, move perishables such as dairy and meat to a cooler or the freezer until the repair is complete.

What is involved in the repair?

We test the fan motor and the board output, then give a written price for whichever part needs replacing. Our labor carries a 30-day warranty.