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Error code reference

Thermador Range Error Code F33

Upper oven over temperature while cooking; also warming drawer sensor failure.

Thermador codesThermador range codes

Upper oven over temperature while cooking; also warming drawer sensor failure.

First step from the service manual

Allow oven to cool below 550°F before turning power on; check header P3; check sensor resistance (~1080 ohms at room temperature); if sensor OK replace power/relay board.

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

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What F33 means on a Thermador range

The F33 error code on a Thermador range indicates one of two related conditions: an upper oven over-temperature event while cooking, or a failure in the warming drawer temperature sensor circuit. In the upper oven context, F33 triggers when the oven's internal temperature exceeds safe operating thresholds, typically above 550 degrees Fahrenheit, which can result from a runaway broil element, a failed relay on the power board allowing continuous heating, or a faulty temperature sensor sending incorrect readings to the control board. In the warming drawer context, the same code surfaces when the sensor circuit is open or shorted, preventing accurate temperature monitoring.

The temperature sensor is central to diagnosing F33 correctly. A properly functioning sensor reads approximately 1080 ohms of resistance at room temperature. If resistance is significantly higher, lower, or infinite, the sensor itself has failed and must be replaced. Wiring and connections also play a role: header P3 on the control board is the designated connection point for the sensor circuit, and a loose, corroded, or damaged connector at P3 can produce the same fault symptoms as a failed sensor without the sensor itself being defective.

If the sensor tests within spec at approximately 1080 ohms and the P3 header connection is secure, the fault most likely originates in the power and relay board. A stuck or failed relay on this board can allow the heating element to remain energized beyond setpoint, causing the over-temperature condition that triggers F33. In this scenario, replacing the power and relay board resolves the fault. Always allow the oven to cool below 550 degrees Fahrenheit before restoring power to prevent the code from immediately retriggering.

Source: manufacturer service documentation.

Common causes of F33

  1. 01

    Faulty upper oven temperature sensor

    Part replacement

    A failed oven temperature sensor can send incorrect readings to the control board, causing it to misread the oven temperature or lose the circuit entirely. Test the sensor resistance at room temperature; a healthy sensor reads approximately 1080 ohms, and a significant deviation confirms the sensor needs replacement.

  2. 02

    Loose or damaged connection at header P3

    Wiring / connection

    Header P3 is the sensor circuit connection point on the control board, and a loose, corroded, or damaged connector here can break the sensor signal without the sensor itself being defective. Inspect and reseat the P3 connector as part of initial diagnostics.

  3. 03

    Failed power and relay board

    Part replacement

    A stuck or defective relay on the power board can allow the heating element to remain energized past the temperature setpoint, creating a true over-temperature condition. If the sensor resistance and P3 connection both check out, the power and relay board is the next component to replace.

  4. 04

    Actual oven over-temperature event

    Part replacement

    A genuine runaway heating situation, such as from a malfunctioning broil element or a relay that failed in the closed position, can drive the oven above 550 degrees Fahrenheit and trigger F33 as a protective shutoff. After cooling, inspect the heating elements for visible damage.

  5. 05

    Warming drawer sensor failure

    Part replacement

    When F33 is associated with the warming drawer, the drawer's temperature sensor circuit may be open or shorted, disrupting feedback to the control board. Testing the warming drawer sensor resistance and inspecting its wiring harness will confirm or rule out this cause.

See the test procedure for each cause

Frequently asked questions about F33

What does F33 mean on a Thermador range?
F33 indicates either an upper oven over-temperature condition detected while cooking, or a failure in the warming drawer temperature sensor circuit. The control board triggers this code as a protective measure when the upper oven exceeds safe temperature limits, typically above 550 degrees Fahrenheit, or when it loses a valid signal from the warming drawer sensor. Diagnosing which condition applies requires checking sensor resistance and the P3 header connection before evaluating the power and relay board.
Is it safe to use my Thermador range when F33 is displayed?
No, you should not continue cooking when F33 is active. The code indicates either a genuine over-temperature event or a sensor failure that prevents the oven from accurately monitoring its own temperature. Either condition means the oven cannot regulate heat safely until the underlying fault is diagnosed and corrected. Turn the range off and allow it to cool completely before any further use or inspection.
Will resetting the power clear the F33 error on a Thermador range?
A power reset may temporarily clear the F33 display, but it will not fix the underlying cause. If the oven is still above 550 degrees Fahrenheit when power is restored, the code will immediately return. Even if the fault clears after cooling, it will reappear the next time the oven is used if the sensor, wiring, or relay board issue is not addressed. A reset is only useful as a first step to confirm whether the fault is intermittent or persistent.
How do I fix the F33 error on a Thermador range?
Start by allowing the oven to cool below 550 degrees Fahrenheit, then restore power and check whether the code returns. Inspect the P3 header connector on the control board for loose or corroded contacts and reseat it if necessary. Test the temperature sensor resistance, which should read approximately 1080 ohms at room temperature; replace the sensor if it reads outside this range. If the sensor and connections are both good, the power and relay board is likely the faulty component and should be replaced.
How much does it cost to repair a Thermador range showing F33?
Repair costs vary depending on which component has failed. A replacement temperature sensor typically runs between 30 and 80 dollars for the part, while a power and relay board can cost anywhere from 150 to 400 dollars or more depending on the model. Adding professional labor, total repair costs commonly range from 150 to 500 dollars. If the fault is simply a loose connector at P3, the repair may cost nothing beyond a service call if a technician is involved.

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