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Error code reference

KitchenAid Oven Error Code F55

Heatsink NTC open or shorted

KitchenAid codesKitchenAid oven codes

Heatsink NTC open or shorted – heat sink temperature is out of range (-40°C to 125°C) for at least 1 second.

First step from the service manual

Failure is cleared when temperature is greater than -40°C or lower than 95°C for 1 second. Switch OFF all loads except IPC power relay.

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

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What F55 means on a KitchenAid oven

The F55 error code on a KitchenAid oven indicates a fault with the heatsink NTC (Negative Temperature Coefficient) thermistor. This sensor is responsible for monitoring the temperature of the electronic control board's heatsink, which is the heat-dissipating component that protects the board's power electronics during operation. The fault triggers when the heatsink temperature falls outside the acceptable operating range of -40°C to 125°C for a continuous period of at least 1 second. The designation "open or shorted" refers to two failure modes: an open circuit produces an artificially low resistance reading (suggesting impossibly cold temperatures), while a short circuit drives resistance to near zero (suggesting dangerously high temperatures).

When F55 is active, the control board interprets the sensor signal as either far below -40°C or above 95°C, which are the threshold boundaries used to clear the fault. The first diagnostic step involves switching off all loads connected to the board except the IPC (Intelligent Power Control) power relay. This isolates the heatsink thermistor circuit from other electrical loads so the sensor reading can be evaluated independently. If the temperature reading returns to within the valid range after this step, the fault clears automatically.

Common causes include a failed NTC thermistor, damaged wiring between the sensor and the control board, or a failing control board itself. Physical damage to the heatsink or poor thermal contact between the heatsink and the board can also drive temperatures outside the acceptable range, triggering the fault through an actual over-temperature condition rather than a sensor failure.

Source: manufacturer service documentation.

Common causes of F55

  1. 01

    Failed heatsink NTC thermistor

    Part replacement

    The NTC thermistor itself has failed open or shorted, sending an out-of-range resistance signal to the control board. A multimeter check of the sensor's resistance at room temperature will reveal whether it has drifted far outside its expected value or reads open/zero.

  2. 02

    Damaged or disconnected wiring harness

    Wiring / connection

    The wiring between the heatsink thermistor and the control board may have a break, a loose connector, or heat-damaged insulation causing an intermittent open or short. Visually inspecting the harness and checking continuity at the connector pins will identify this issue.

  3. 03

    Actual heatsink over-temperature condition

    Wiring / connection

    If the heatsink is genuinely overheating due to poor thermal contact, blocked ventilation, or a cooling fan failure, the thermistor may be reading accurately and reporting a real over-temperature event above 95°C. Check for obstructions around the control board area and verify any cooling fan is operating.

  4. 04

    Faulty electronic control board

    Part replacement

    If the thermistor and wiring both check out correctly, the control board's input circuit for the NTC signal may have failed internally, causing it to misinterpret a valid sensor reading as out of range. Board replacement is required in this scenario.

See the test procedure for each cause

Frequently asked questions about F55

What does F55 mean on a KitchenAid oven?
F55 indicates that the heatsink NTC thermistor on the electronic control board is reporting a temperature outside the acceptable range of -40°C to 125°C for at least 1 second. This sensor monitors the heat-dissipating component on the control board to protect the oven's electronics. The fault can be triggered by a failed sensor, a wiring problem, or an actual over-temperature condition. The oven's control system will clear the code automatically once the reading returns to within the valid range.
Can I fix F55 on my KitchenAid oven myself?
Some steps are DIY-friendly, such as checking for loose connectors at the heatsink thermistor and ensuring ventilation around the control board is not blocked. However, testing the NTC thermistor with a multimeter and evaluating the control board requires basic electrical knowledge and comfort working around oven electronics with the power disconnected. If the thermistor or control board needs replacement, a qualified technician is recommended to ensure the repair is done safely and correctly.
Is it safe to use my KitchenAid oven when F55 is displayed?
It is not recommended to continue using the oven while F55 is active. The code indicates the control board cannot reliably monitor its own heatsink temperature, which means the electronics may be operating without adequate thermal protection. Continued use could potentially damage the control board further or create an unsafe condition if an actual over-temperature situation is being masked.
Will resetting my KitchenAid oven clear the F55 error?
The F55 fault is designed to clear automatically when the heatsink temperature reading returns to within the valid range, specifically above -40°C or below 95°C for at least 1 second. Cutting power to the oven and restoring it may temporarily clear the display, but if the underlying cause is a failed thermistor or damaged wiring, the code will return. A reset alone does not fix the root problem.
How much does it cost to repair a KitchenAid oven F55 error?
Repair cost depends on what component has failed. A heatsink NTC thermistor is generally an inexpensive part, with replacement costs typically ranging from $50 to $150 including labor. If the electronic control board itself requires replacement, costs can range from $200 to $500 or more depending on the model and labor rates in your area. Getting a diagnostic inspection first will clarify which component is at fault before committing to a repair.

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