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Error code reference

Whirlpool Microwave Error Code NTC OPEN, CALL FOR SERVICE

Hood NTC thermistor has an open circuit condition.

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Hood NTC thermistor has an open circuit condition.

First step from the service manual

Unplug microwave oven or disconnect power. Measure hood thermistor resistance; 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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  • Step-by-step tests with expected resistance, voltage, and continuity values
  • Wiring diagram references and connector pinouts from the OEM service manual
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What NTC OPEN, CALL FOR SERVICE means on a Whirlpool microwave

The NTC OPEN, CALL FOR SERVICE error on a Whirlpool microwave indicates that the hood NTC (Negative Temperature Coefficient) thermistor has developed an open circuit condition. The hood thermistor is a temperature-sensing resistor mounted in the ventilation area of the microwave hood assembly. Its job is to monitor ambient or exhaust temperatures in the hood section and relay that data to the control board. When the circuit reads as open, the control board receives no valid signal from the thermistor, and as a safety measure, it halts operation and displays this fault code.

An NTC thermistor should measure approximately 10,000 ohms (10K ohms) at 77°F (25°C), with a tolerance of plus or minus 5%. As temperature rises, the resistance of an NTC thermistor decreases. An open circuit reading means resistance has gone effectively infinite, which the control board interprets as a sensor failure rather than a real temperature condition. This type of failure is distinct from a short circuit, where resistance would drop toward zero.

The most reliable way to diagnose this fault is to disconnect power from the unit and use a digital multimeter to measure resistance across the thermistor terminals. A reading far outside the 10K ohm range at room temperature confirms the component has failed. However, technicians should also inspect the wiring harness and connector between the thermistor and the control board, since an open circuit can result from a broken wire or corroded connector rather than a failed thermistor itself.

Source: manufacturer service documentation.

Common causes of NTC OPEN, CALL FOR SERVICE

  1. 01

    Failed hood thermistor

    Part replacement

    The thermistor itself has burned out or degraded internally, breaking the circuit. A multimeter reading far above 10K ohms at room temperature confirms the component needs replacement.

  2. 02

    Broken or disconnected wiring harness

    Wiring / connection

    The wire leads connecting the thermistor to the control board may have cracked, pulled loose from a connector, or broken due to heat exposure or physical stress. Visually inspect the harness and connectors for damage or separation.

  3. 03

    Corroded or damaged connector terminals

    Wiring / connection

    Moisture or grease in the hood area can cause the thermistor connector terminals to corrode, creating an open circuit even when the thermistor itself is intact. Inspect the connector pins for oxidation or physical damage.

  4. 04

    Heat damage to thermistor or leads

    Part replacement

    Prolonged exposure to high temperatures, such as from heavy cooking or a ventilation blockage, can degrade the thermistor or melt insulation on its leads. Signs include discoloration or brittle wiring near the sensor.

  5. 05

    Faulty control board

    Part replacement

    In rare cases, the control board itself may have a defective input circuit that misreads the thermistor signal as an open condition even when the thermistor measures correctly. This is the least likely cause and should only be considered after confirming the thermistor and wiring are in good condition.

See the test procedure for each cause

Frequently asked questions about NTC OPEN, CALL FOR SERVICE

What does NTC OPEN, CALL FOR SERVICE mean on a Whirlpool microwave?
This error code means the control board has detected an open circuit in the hood NTC thermistor circuit. The thermistor is a temperature sensor in the hood section of the microwave that should measure approximately 10K ohms at room temperature. When the circuit reads as open, the board cannot receive a valid temperature signal and shuts down the unit. The fault must be diagnosed and repaired before the microwave will operate again.
Can I fix the NTC OPEN error myself, or do I need a technician?
A knowledgeable DIYer can perform the initial diagnosis by unplugging the unit and using a multimeter to check the thermistor resistance against the 10K ohm specification. If the wiring or connector is simply disconnected, reattaching it may resolve the issue without new parts. However, if the thermistor itself has failed or wiring is damaged inside the hood assembly, the repair involves disassembling the unit and sourcing the correct replacement part, which many homeowners prefer to leave to a technician.
Will resetting the microwave clear the NTC OPEN error code?
Unplugging the microwave and restoring power may temporarily clear the display, but the error code will return immediately if the underlying open circuit condition still exists. The fault is not a random software glitch. The only way to permanently clear the code is to repair or replace the faulty thermistor or wiring causing the open circuit.
Is it safe to use my Whirlpool microwave while this error is showing?
No. The hood thermistor is part of the appliance's thermal monitoring system. When this error is active, the microwave has disabled itself because it cannot confirm safe operating temperatures in the hood area. Attempting to bypass or ignore this fault and continue using the unit is not recommended, as the appliance cannot properly detect overheating conditions.
How much does it cost to repair the NTC OPEN error on a Whirlpool microwave?
Repair costs vary depending on whether the issue is a wiring problem or a failed thermistor. A replacement thermistor is generally an inexpensive part, typically in the range of $10 to $40 depending on the model. If a technician performs the diagnosis and repair, labor costs will add to that total, with overall repair estimates commonly ranging from $80 to $200. If the control board is the root cause, costs will be higher.

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