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Error code reference

Whirlpool Microwave Error Code NTC OPEN

HF NTC thermistor is open (displayed as 'NTC OPEN, CALL FOR SERVICE' scrolling on display).

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HF NTC thermistor is open (displayed as 'NTC OPEN, CALL FOR SERVICE' scrolling on display).

First step from the service manual

Unplug microwave oven or disconnect power. Measure HF NTC thermistor; normal is 10k ohms +/- 5% at 77°F (25°C).

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

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What NTC OPEN means on a Whirlpool microwave

The NTC OPEN error code on a Whirlpool microwave indicates that the HF (High Frequency) NTC thermistor has developed an open circuit condition. NTC stands for Negative Temperature Coefficient, meaning the thermistor's resistance decreases as temperature rises. This component monitors the temperature of the high-frequency components in the microwave, typically including the magnetron and surrounding circuitry. When the control board detects an open circuit instead of the expected resistance reading, it halts operation and scrolls the message 'NTC OPEN, CALL FOR SERVICE' across the display as a protective measure.

The thermistor's normal resistance value is 10k ohms, plus or minus 5%, at 77 degrees Fahrenheit (25 degrees Celsius). An open circuit means the resistance has climbed far beyond that range, effectively breaking the circuit. This prevents the control board from receiving any temperature feedback, so the unit shuts down rather than risk overheating critical components. The fault must be addressed before the microwave will resume normal operation.

The most common causes include a failed thermistor, damaged wiring or connectors in the thermistor circuit, or a poor solder joint on the thermistor itself. Physical damage from heat exposure, moisture intrusion, or simple age-related component failure can all produce an open thermistor reading. Diagnosis begins with disconnecting power and measuring the thermistor resistance directly with a multimeter to confirm whether the component itself has failed or whether a wiring fault exists elsewhere in the circuit.

Source: manufacturer service documentation.

Common causes of NTC OPEN

  1. 01

    Failed HF NTC Thermistor

    Part replacement

    The thermistor itself has burned out or broken internally, creating an open circuit. Measuring it with a multimeter will show resistance far above the expected 10k ohms at room temperature, or no continuity at all.

  2. 02

    Damaged Wiring or Connector

    Wiring / connection

    The wire harness or connector linking the thermistor to the control board may be broken, corroded, or disconnected. Visually inspect the wiring for burns, breaks, or loose connector pins after disconnecting power.

  3. 03

    Heat Damage to Thermistor or Circuit

    Part replacement

    Prolonged exposure to high operating temperatures can degrade the thermistor or the solder joints securing it to the circuit board. Look for discoloration or visible burn marks near the component.

  4. 04

    Moisture or Contamination

    Wiring / connection

    Moisture or food debris entering the microwave cavity area can corrode thermistor leads or connector contacts over time, causing intermittent or permanent open circuit conditions.

  5. 05

    Control Board Fault

    Part replacement

    In less common cases, the control board itself may be misreading the thermistor circuit. This is typically only suspected after confirming the thermistor measures correctly at 10k ohms plus or minus 5% at 77 degrees Fahrenheit and the wiring checks out.

See the test procedure for each cause

Frequently asked questions about NTC OPEN

What does NTC OPEN mean on a Whirlpool microwave?
NTC OPEN means the control board has detected an open circuit in the HF NTC thermistor, which is the temperature sensor that monitors the high-frequency components including the magnetron. The display scrolls the message 'NTC OPEN, CALL FOR SERVICE' to alert you to the fault. The microwave shuts down as a protective measure because it can no longer monitor component temperatures. The thermistor's expected resistance is 10k ohms, plus or minus 5%, at 77 degrees Fahrenheit.
Can I fix the NTC OPEN error myself?
A knowledgeable DIYer can begin by unplugging the microwave and measuring the HF NTC thermistor with a multimeter to confirm whether the component has failed. If the thermistor reads open or far outside the 10k ohm specification, replacing it is a straightforward parts swap. However, microwaves contain high-voltage capacitors that can retain a dangerous charge even after unplugging, so proper discharge procedures must be followed before touching internal components.
Is it safe to use my Whirlpool microwave with the NTC OPEN error showing?
No, the microwave should not be used while this error is active. The NTC thermistor is a safety component that protects against overheating, and the unit will not operate normally while the fault is present. Attempting to bypass the error without repairing the underlying cause could risk damage to internal components.
How much does it cost to repair the NTC OPEN error on a Whirlpool microwave?
If only the thermistor needs replacement, parts costs are generally in the range of $10 to $40 depending on the specific model. If a professional technician is needed, expect total repair costs including labor to fall somewhere between $80 and $200. Control board replacement, if required, can push costs higher and may factor into a repair-versus-replace decision.
Will resetting my Whirlpool microwave clear the NTC OPEN error?
Unplugging the microwave and restoring power may temporarily clear the display, but the error will return as soon as the control board checks the thermistor circuit again and detects the open condition. A reset does not fix the underlying hardware fault. The thermistor or its wiring must be repaired or replaced for the error to clear permanently.

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