Sub-Zero 700TF Code 88: Board and compressor controller not talking

What 88 means

On 700 Series 700TF-2 and 700TF-3 units with a variable-speed compressor, the 700TFI among them, code 88 means the serial communication between the control board and the VS compressor controller has failed. One known cause is lead orientation, so the connection between them should be checked. The code may appear right after a control board replacement. Without that link, the compressor may not run and the unit warms.

Common causes of 88

Communication leads connected in the wrong orientation
Loose serial connection between the board and the VS controller
VS compressor controller or control board not communicating

✓ One safe check you can try

1. Note code 88 and when it first appeared. 2. Tell us whether the control board was replaced recently. 3. Give the control a fresh start by keeping the breaker off for two minutes. 4. Keep doors closed and watch temperatures with a thermometer in each section. 5. Call us if code 88 remains.

! Why to stop there

The leads sit in the machine compartment beside line voltage.
Reversing or reseating connections needs the unit powered down correctly.
Testing serial communication requires service tools.

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

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 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

8888 questions

Why did code 88 show up after a board replacement?

If the communication leads were plugged in with the wrong orientation, the new board and the VS compressor controller cannot talk. Checking lead orientation is one of the first steps.

Does code 88 mean the compressor is bad?

No. It concerns the serial link between the board and the controller. The compressor itself may be perfectly fine once communication is restored between the two.

What does the repair involve?

We check lead orientation and the connection, then test the board and controller if needed. You get a written price before any part is replaced.