Sub-Zero Classic BI Code 90-3-38: Condenser output on the board

What 90-3-38 means

Classic BI refrigerators like the BI-36U/S and BI-48SD/S report 90-3-38 for a condenser FET power output error. The FET is a switch on the control board that powers the condenser side; this code says that output is not working as expected. Without proper condenser airflow, the unit can struggle to shed heat, so temperatures may rise and the compressor may run longer.

Common causes of 90-3-38

Control board FET output to the condenser not switching
Condenser fan wiring loose or damaged
Condenser fan drawing incorrectly on that output

✓ One safe check you can try

1. Clean the grille opening with a soft brush or vacuum so the condenser can breathe. 2. Keep rugs, bags and boxes away from the grille. 3. Restart power at the breaker for one minute. 4. Watch temperatures with a thermometer and call us if the code returns.

! Why to stop there

Board outputs must be tested with power applied.
The condenser area has hot surfaces and moving parts.
Replacing a board requires correct setup for the model.

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

90-3-3890-3-38 questions

What does a FET output do?

A FET is a small electronic switch on the BI control board that powers a load. With 90-3-38, the output feeding the condenser side is not working correctly, so condenser airflow may be affected.

Can cleaning the condenser help?

Cleaning helps airflow and is always worth doing, but this code is about the board output itself. If 90-3-38 returns after cleaning and a restart, the board or the wiring needs testing.

How is it fixed?

We test the condenser output on the board and the wiring to the condenser, then quote in writing before replacing anything. Labor is covered by our 30-day workmanship warranty.