Sub-Zero Ice Maker Error Code Slow flashing light

A slow flashing indicator light on a Sub-Zero ice maker indicates that the control board has detected an open or disconnected liquid line thermistor. This thermistor is a temperature sensor mounted on the refrigerant liquid line that the control board relies on to monitor temperatures during the ice-making cycle. When the sensor signal is lost or the circuit is open, the slow flash fault code is triggered. The ice maker will not operate normally until the fault is resolved.

A simple reset will not permanently clear this fault if the underlying problem with the liquid line thermistor has not been corrected. The slow flashing light is a hardware fault code tied to a specific sensor condition, and the control board will re-trigger the alert as long as the thermistor circuit remains open or out of specification. Address the thermistor connection or replace the sensor before attempting a reset.

Repair costs vary depending on the root cause. If the fix involves simply reseating a loose connector, there may be no parts cost and only a service call fee, typically in the range of $75 to $150. If the liquid line thermistor itself needs replacement, parts and labor combined can range from $150 to $350 or more depending on your location and the technician's rates. Inspecting the connector and wiring first is always recommended before purchasing replacement parts.

Start by checking the thermistor wire connector at the control board and firmly reseating it if it is loose. Next, use a multimeter to measure thermistor resistance: you should read approximately 30K to 33K ohms at 32 degrees Fahrenheit or 8K to 12K ohms at 77 degrees Fahrenheit. If the readings fall outside these ranges, the thermistor needs to be replaced. Also inspect the wire harness running from the thermistor to the board for any breaks or damage.

It is not advisable to continue running the ice maker while this fault is active. Without a functioning liquid line thermistor, the control board lacks accurate temperature data needed to manage the ice-making cycle properly. Continued operation under these conditions can lead to inefficient cycling or potential damage to other components. Resolving the thermistor fault first ensures the unit operates within its intended parameters.