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Error code reference

Hotpoint Cooktop Error Code F05

ISI UART 1 (CN 03) inductor NTC fault on large induction hotplate

Hotpoint codesHotpoint cooktop codes

ISI UART 1 (CN 03) inductor NTC fault on large induction hotplate — subcode 1: NTC short circuit; subcode 2: NTC open circuit; subcode 3: large induction hotplate not connected.

First step from the service manual

Check the inductor, verifying that the contacts are well connected and clean.

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

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What F05 means on a Hotpoint cooktop

The F05 error code on a Hotpoint induction cooktop indicates a fault in the NTC (Negative Temperature Coefficient) thermistor associated with the large induction hotplate inductor, monitored through the ISI UART 1 communication channel on connector CN 03. The NTC thermistor is a temperature-sensing component embedded in or near the inductor coil of the large induction zone. It continuously monitors inductor temperature to protect the coil and power electronics from overheating. When the control board loses a valid signal from this sensor, it triggers F05 and disables the affected zone.

The error is subdivided into three specific subcodes that identify the nature of the fault. Subcode 1 indicates the NTC is reading a short circuit condition, which typically produces a resistance value far below the expected range and signals an extremely high (or falsely reported) temperature. Subcode 2 indicates an open circuit condition, where the NTC circuit is broken and no resistance reading is possible, often caused by a broken wire, failed solder joint, or a thermistor that has burned out internally. Subcode 3 indicates that the large induction hotplate assembly itself is not detected as connected, pointing to a wiring harness or connector issue between the inductor and the control board.

The first diagnostic step is to inspect the inductor assembly and its associated wiring at connector CN 03. Contacts should be checked for corrosion, debris, or looseness. A secure and clean connection at this connector is essential for proper NTC signal transmission. If the connector checks out, the NTC thermistor itself and the inductor coil wiring should be tested for continuity and correct resistance values to isolate whether the fault is in the sensor, the harness, or the inductor assembly.

Source: manufacturer service documentation.

Common causes of F05

  1. 01

    Loose or corroded connector at CN 03

    Wiring / connection

    The CN 03 connector linking the inductor and NTC to the control board can work loose over time or develop oxidation on its contacts. This is the first thing to check, as a poor connection can trigger any of the three subcodes.

  2. 02

    Failed NTC thermistor (open circuit)

    Part replacement

    The NTC thermistor itself can fail internally, breaking the circuit and producing an open circuit reading. This corresponds to subcode 2 and requires replacing the thermistor or the inductor assembly if the sensor is not serviced separately.

  3. 03

    Shorted NTC thermistor

    Part replacement

    A thermistor that has shorted internally will present a resistance reading far outside the normal range, triggering subcode 1. This typically occurs after an overheating event or due to component aging.

  4. 04

    Damaged or broken wiring harness

    Part replacement

    Wires running between the inductor NTC and the control board can fray, crack, or break, especially near connectors or where harnesses are routed near heat sources. A break in the harness will register as an open circuit or a disconnected hotplate.

  5. 05

    Large induction hotplate not connected (subcode 3)

    Wiring / connection

    If the inductor assembly was recently serviced or the unit was moved, the hotplate connector may not be fully seated. Subcode 3 specifically indicates the control board cannot detect the large inductor as connected.

See the test procedure for each cause

Frequently asked questions about F05

What does F05 mean on a Hotpoint cooktop?
F05 indicates a fault with the NTC temperature sensor on the large induction hotplate, monitored via the ISI UART 1 channel at connector CN 03. The error has three subcodes: a short circuit in the NTC, an open circuit in the NTC, or the large induction hotplate not being detected as connected. The affected burner zone will be disabled until the fault is corrected.
Can I fix the F05 error myself on my Hotpoint induction cooktop?
Some cases of F05 can be resolved without parts by inspecting and reseating the CN 03 connector and cleaning any corroded contacts. However, if the NTC thermistor or wiring harness has failed, those components will need to be replaced. Working inside an induction cooktop involves capacitors that can hold dangerous charge even when unplugged, so technicians with appliance repair experience are strongly recommended for any internal inspection.
Is it safe to use my Hotpoint cooktop while F05 is displayed?
When F05 is active, the large induction hotplate zone is disabled by the control board as a safety measure, so it will not heat. Other zones may continue to function depending on the cooktop model. You should not attempt to bypass this fault, as the NTC thermistor is a critical thermal protection component for the inductor.
Will resetting my Hotpoint cooktop clear the F05 error?
Powering the cooktop off at the circuit breaker and back on may temporarily clear the display, but F05 will return if the underlying fault with the NTC sensor or connector has not been resolved. A reset does not repair a failed thermistor, broken wire, or loose connector. The root cause must be diagnosed and corrected for the error to stay clear.
How much does it cost to repair a Hotpoint cooktop showing F05?
Repair costs vary depending on the fault. If the issue is only a loose or dirty connector, there may be no parts cost and a minimal labor charge. If the NTC thermistor or inductor assembly requires replacement, parts alone can range from around 30 to 150 dollars or more, with labor adding to the total. A service call for diagnosis typically runs between 75 and 150 dollars before any parts are factored in.

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