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Error code reference

Polar Refrigerator Error Code Thermistor Fault

The thermistor has been sensed as inoperable; temperature is being controlled via backup operating system

Polar codesPolar refrigerator codes

The thermistor has been sensed as inoperable; temperature is being controlled via backup operating system. Green flashes off every 20 sec (AC mode) or Amber flashes off every 20 sec (Gas mode) on N7V/N8V; temperature setting snowflakes flash on N7X/N8X.

First step from the service manual

Verify thermistor wire is plugged in; check wire assembly and connector for broken/dirty connections.

The complete diagnostic procedure includes additional test steps, resistance specifications, wiring diagram references, and component test points.

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What Thermistor Fault means on a Polar refrigerator

The Thermistor Fault on a Polar refrigerator indicates that the control system has detected the thermistor as inoperable. The thermistor is a temperature-sensing resistor that feeds real-time cabinet temperature data to the refrigerator's control board. When this sensor fails or loses its connection, the unit cannot accurately monitor internal temperatures through its primary sensing circuit. In response, the refrigerator automatically switches to a backup operating mode to maintain basic temperature control while the fault is active.

The way this fault displays depends on the specific Polar model. On N7V and N8V models, the LED indicator light will flash off briefly every 20 seconds, with the color indicating the current operating mode: green for AC power mode or amber for gas mode. On N7X and N8X models, the temperature setting snowflake icons on the display will flash to signal the fault condition. In both cases, the unit continues to operate in a reduced-capacity backup mode, meaning cooling is maintained but precise temperature regulation is compromised.

The most common causes involve the physical connection between the thermistor and the control board rather than thermistor component failure itself. A disconnected plug, corroded connector terminals, or a damaged wire harness can all interrupt the signal and trigger this fault. Because the thermistor relies on a continuous low-resistance circuit to report accurate readings, even a partially broken connection or contaminated contact point is enough to cause the control board to interpret the sensor as inoperable.

Source: manufacturer service documentation.

Common causes of Thermistor Fault

  1. 01

    Disconnected thermistor connector

    Wiring / connection

    The thermistor wire plug may have come loose from its socket on the control board or at the sensor itself. Inspect both ends of the thermistor wiring harness and firmly reseat any loose connectors.

  2. 02

    Corroded or dirty connector contacts

    Wiring / connection

    Moisture and condensation inside a refrigerator can cause connector terminals to corrode or accumulate debris, interrupting the sensor signal. Visually inspect the connector pins for oxidation or contamination and clean as needed.

  3. 03

    Damaged wire harness

    Part replacement

    The wiring between the thermistor and the control board may have a break, pinch, or chafed section that interrupts continuity. Trace the full length of the wire assembly and look for visible damage.

  4. 04

    Failed thermistor

    Part replacement

    The thermistor itself may have failed internally, presenting an out-of-range or open resistance reading to the control board. If wiring and connections check out, the thermistor should be tested for proper resistance values and replaced if faulty.

  5. 05

    Control board fault

    Part replacement

    In rare cases, the control board's thermistor input circuit may be faulty, causing it to misread a properly functioning sensor. This is typically only considered after all wiring and the thermistor have been confirmed good.

See the test procedure for each cause

Frequently asked questions about Thermistor Fault

What does Thermistor Fault mean on a Polar refrigerator?
This fault means the refrigerator's control system has detected that the thermistor, the internal temperature sensor, is inoperable. The unit responds by switching to a backup operating mode to continue cooling while the fault is present. On N7V and N8V models, the indicator light flashes off every 20 seconds in green (AC mode) or amber (gas mode). On N7X and N8X models, the temperature snowflake icons on the display will flash.
How do I fix a Thermistor Fault on a Polar refrigerator?
Start by checking that the thermistor wire is fully plugged in at both the sensor and control board ends. Inspect the entire wire harness and connector for broken wires, bent pins, or dirty contacts and clean or reseat as needed. If the connections are all secure and intact, test the thermistor itself for the correct resistance and replace it if it has failed.
Is my Polar refrigerator safe to use while showing a Thermistor Fault?
The refrigerator does continue to operate in a backup mode during this fault, so it is still cooling. However, precise temperature regulation is compromised, which means the cabinet temperature may not be held as accurately as normal. Food safety could be at risk if the backup mode does not maintain adequate temperatures over time, so the fault should be resolved as soon as possible.
Will resetting my Polar refrigerator clear the Thermistor Fault?
A power reset may temporarily clear the fault display, but if the underlying cause, such as a loose connector, damaged wire, or failed thermistor, is still present, the fault will return. The fault code will only clear permanently once the faulty component or connection has been found and corrected.
How much does it cost to repair a Thermistor Fault on a Polar refrigerator?
If the fix is simply reseating a connector or cleaning corroded terminals, there may be no parts cost involved, with only a service call fee if a technician is used. Replacing a thermistor is generally an inexpensive repair, with parts typically ranging from $10 to $50 depending on the model. If a damaged wire harness or control board is involved, repair costs will be higher, potentially ranging from $80 to $300 or more including labor.

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