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Error code reference

Hotpoint Cooktop Error Code F15

ISI UART 1 (CN 04)

Hotpoint codesHotpoint cooktop codes

ISI UART 1 (CN 04): Excessively high temperature on the small induction coil.

First step from the service manual

Check whether the induction coil NTC has become miscalibrated.

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

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What F15 means on a Hotpoint cooktop

The F15 error code on a Hotpoint induction cooktop indicates that the ISI UART 1 communication channel, connected via the CN 04 connector, has detected an excessively high temperature on the small induction coil. The induction coil uses an NTC (Negative Temperature Coefficient) thermistor to monitor operating temperature in real time. As temperature rises, the NTC's resistance decreases in a predictable curve, and the control board uses that resistance reading to determine whether the coil is within safe operating limits. When the reported temperature exceeds the acceptable threshold, the board triggers F15 to prevent damage to the coil windings or surrounding components.

The most common cause is NTC miscalibration or drift, where the thermistor begins reporting temperature values that no longer accurately reflect actual coil conditions. A miscalibrated NTC may report falsely high temperatures even when the coil is operating normally, or it may have degraded due to prolonged heat exposure, causing its resistance-to-temperature curve to shift. This results in the control board interpreting normal operating conditions as an over-temperature fault.

Beyond NTC miscalibration, actual overheating of the small induction coil is also a real possibility. Blocked ventilation, a failed cooling fan, or heavy sustained use can allow coil temperatures to genuinely exceed safe limits. The CN 04 connector and associated wiring should also be inspected, as a loose or corroded connection can introduce signal errors that mimic an over-temperature condition at the control board level.

Source: manufacturer service documentation.

Common causes of F15

  1. 01

    Miscalibrated or drifted NTC thermistor

    Part replacement

    The NTC thermistor monitoring the small induction coil can drift out of its correct resistance-to-temperature curve over time, causing the control board to read falsely elevated temperatures. This is the first component to check and is a frequent source of this fault.

  2. 02

    Failed or degraded NTC thermistor

    Part replacement

    The NTC thermistor may have failed outright due to heat stress or age, producing out-of-range resistance readings. Measuring the thermistor's resistance and comparing it against the expected values for a given temperature will confirm this fault.

  3. 03

    Actual induction coil overheating

    Wiring / connection

    If ventilation around the cooktop is blocked, or if the cooling fan has failed, the small induction coil can genuinely reach excessive temperatures and trigger F15. Check for obstructions around the appliance and verify the cooling fan is operating correctly.

  4. 04

    Loose or corroded CN 04 connector

    Wiring / connection

    The CN 04 connector carries the NTC signal to the ISI UART 1 channel. A loose pin, corrosion, or a damaged connector housing can introduce resistance or signal noise that the board interprets as an over-temperature reading. Inspect and reseat the connector.

  5. 05

    Faulty induction control board

    Part replacement

    If the NTC thermistor, wiring, and connector all test correctly, the control board itself may be misreading the incoming signal. A board fault is the least common cause but should be considered after other components are ruled out.

See the test procedure for each cause

Frequently asked questions about F15

What does F15 mean on a Hotpoint cooktop?
F15 indicates that the ISI UART 1 channel, operating through the CN 04 connector, has detected an excessively high temperature on the small induction coil. The cooktop monitors coil temperature using an NTC thermistor, and this code is triggered when that reading exceeds safe limits. The fault may reflect either a genuine overheating condition or a miscalibrated sensor. The cooktop will not operate normally until the underlying cause is resolved.
Can I fix the F15 error myself, or do I need a technician?
Some steps, like clearing ventilation blockages around the cooktop or reseating the CN 04 connector, can be done without specialized tools. However, testing and replacing the NTC thermistor or diagnosing the control board requires a multimeter and familiarity with induction cooktop components. If you are not comfortable working with appliance electronics, a qualified technician is the safer choice.
Is it safe to keep using the cooktop while the F15 code is displayed?
No. The F15 code signals a potential overheating condition on the induction coil, and continuing to use the cooktop before diagnosing the fault could risk damage to the coil windings or other internal components. Stop using the appliance and allow it to cool completely before attempting any inspection.
Will resetting the cooktop clear the F15 error?
A reset may temporarily clear the fault display, but if the underlying problem persists, whether a miscalibrated NTC, a failed thermistor, or a cooling issue, the F15 code will return during operation. Resetting without repairing the root cause does not resolve the fault and may mask a real overheating risk.
How much does it cost to repair an F15 error on a Hotpoint induction cooktop?
Repair costs vary depending on the faulty component. Replacing an NTC thermistor is generally the least expensive fix, typically in the range of $20 to $80 for the part. If the control board requires replacement, costs can range from $150 to $350 or more depending on the specific board and labor rates in your area. Getting a diagnostic assessment first will help determine the most cost-effective path forward.

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