Sub-Zero Refrigerator Error Code 43

Error code 43 on a Sub-Zero refrigerator indicates a fault detected in the left refrigerant valve circuit. This valve, manufactured by Aweco, is an electrically actuated solenoid valve that controls the flow of refrigerant within the sealed system. Sub-Zero units commonly use a dual-refrigeration or multi-zone cooling architecture, where individual refrigerant valves direct refrigerant to specific evaporators or cooling circuits. When the control board detects an out-of-range signal, an open circuit, or a short in the left valve circuit, it logs error code 43 and may restrict or alter cooling operation.

The Aweco refrigerant valve operates via a solenoid coil that opens or closes based on signals from the main control board. A fault can originate at the valve coil itself, in the wiring harness connecting the valve to the board, or at the connector pins. Coil failures often present as an open circuit when measured with a multimeter, while wiring faults may appear as intermittent resistance readings or visible damage such as chafing or corrosion at connectors.

Diagnosing this error requires a systematic inspection of the Aweco valve and its associated wiring. Technicians should begin by visually examining the wiring harness for damaged insulation, corroded terminals, or loose connector fits. If wiring appears intact, the valve coil resistance should be measured and compared against the expected specification. A reading of infinite resistance confirms an open coil, while a very low reading may indicate a shorted coil. Both conditions require valve replacement to resolve the fault.