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Error code reference

Hotpoint Cooktop Error Code F13

ISI UART 2 (CN 04)

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ISI UART 2 (CN 04): Excessively high heatsink temperature.

First step from the service manual

Check that the fan is properly wired and cables are intact.

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

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What F13 means on a Hotpoint cooktop

The F13 error code on a Hotpoint cooktop indicates an excessively high heatsink temperature detected by the ISI UART 2 module, which communicates through connector CN 04. The ISI (Induction System Interface) module manages power delivery and thermal regulation for the induction cooking zones. The heatsink is a critical thermal management component that dissipates heat generated by the IGBT transistors and power electronics. When the heatsink temperature climbs beyond safe operating thresholds, the control system triggers this fault to prevent permanent damage to the power electronics.

The primary cooling mechanism for the heatsink is a dedicated cooling fan. If this fan is not operating correctly, heat accumulates rapidly in the electronics compartment, causing the thermal sensor to register an over-temperature condition. Wiring faults, a disconnected fan harness, or a mechanically failed fan motor are among the most direct causes. The first diagnostic step specifically targets this: confirming the fan is properly connected and that all associated cables are intact and undamaged.

Beyond the fan itself, restricted airflow through blocked ventilation openings or a contaminated heatsink surface can also trigger F13. In some cases, a failed thermal sensor or a fault within the ISI UART 2 module itself may produce a false over-temperature reading even when the actual heatsink temperature is within normal range. Diagnosis should proceed from the simplest mechanical checks, such as fan wiring and airflow, before moving toward electronic component evaluation.

Source: manufacturer service documentation.

Common causes of F13

  1. 01

    Disconnected or damaged fan wiring

    Wiring / connection

    The cooling fan harness may have become loose at the connector CN 04 or sustained damage to the cable. Inspect the wiring for fraying, pinched sections, or a connector that has pulled free from its socket.

  2. 02

    Failed cooling fan motor

    Part replacement

    The fan motor itself may have seized or burned out, preventing airflow across the heatsink entirely. Manually spin the fan blade with power disconnected to check for resistance or binding, and verify the fan runs when power is restored.

  3. 03

    Blocked or restricted ventilation

    Wiring / connection

    Grease buildup, debris, or an obstructed vent opening can reduce airflow even if the fan is running. Clean the ventilation openings and inspect the heatsink fins for contamination that would impede heat transfer.

  4. 04

    Faulty heatsink temperature sensor

    Part replacement

    A defective thermal sensor on the heatsink may report an over-temperature condition inaccurately. If the fan and airflow check out normally, the sensor should be tested for proper resistance values consistent with the cooktop's operating temperature.

  5. 05

    Failed ISI UART 2 module

    Part replacement

    If all external components including the fan, wiring, and airflow are confirmed to be functioning correctly, the ISI UART 2 control module connected at CN 04 may have an internal fault causing it to misread or falsely trigger the over-temperature alarm.

See the test procedure for each cause

Frequently asked questions about F13

What does F13 mean on a Hotpoint cooktop?
F13 indicates that the heatsink inside the cooktop's induction electronics has reached an excessively high temperature, as detected by the ISI UART 2 module at connector CN 04. The cooktop shuts down automatically to protect its internal power components. This fault is most commonly related to the cooling fan or its wiring. Addressing the fan circuit is the recommended first step in diagnosis.
Can I fix the F13 error myself or do I need a technician?
Some causes of F13 are accessible to a knowledgeable DIYer, particularly checking that the cooling fan is properly connected and that ventilation openings are clear of debris. However, testing electronic components like the ISI UART 2 module or replacing the fan motor requires comfort working with appliance electronics and basic diagnostic tools. If you are not confident working inside the cooktop, a qualified appliance technician is recommended.
Is it safe to keep using my Hotpoint cooktop when F13 is showing?
No, you should not continue using the cooktop while F13 is active. The error indicates that critical power electronics are overheating, and operating the cooktop in this condition can cause permanent damage to internal components. In rare cases, sustained overheating of electronics can also present a safety risk. Leave the cooktop off until the fault has been properly diagnosed and resolved.
Will resetting the cooktop clear the F13 error code?
A power reset may temporarily clear the F13 code, but if the underlying cause such as a faulty fan or blocked airflow has not been corrected, the error will return once the cooktop operates long enough for the heatsink to overheat again. Resetting without repairing the root cause can lead to repeated shutdowns and possible component damage over time.
How much does it cost to repair a Hotpoint cooktop F13 error?
Repair costs vary depending on the cause. If the issue is simply a loose wiring connector, there may be no parts cost involved beyond a service call, which typically ranges from $75 to $150. Replacing a cooling fan motor generally costs between $100 and $250 including parts and labor. If the ISI UART 2 control module requires replacement, costs can range from $200 to $450 or more depending on parts availability and labor rates in your area.

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