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Error code reference

Thermador Cooktop Error Code c3

Radiator temperature failure (cooktop has heated up excessively due to excessive temperature on the radiator).

Thermador codesThermador cooktop codes

Radiator temperature failure (cooktop has heated up excessively due to excessive temperature on the radiator).

First step from the service manual

Disconnect the cooktop from the power grid. If the failure continues, allow to cool.

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

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  • Step-by-step tests with expected resistance, voltage, and continuity values
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What c3 means on a Thermador cooktop

The C3 error code on a Thermador cooktop indicates a radiator temperature failure caused by excessive heat buildup in the cooktop's heating radiator. This code is triggered when an internal temperature sensor detects that the radiator has surpassed its safe operating threshold. The cooktop's control system monitors radiator temperature continuously during operation, and when that temperature exceeds design limits, the unit shuts down and displays C3 to prevent further damage to internal components.

The most immediate cause of this condition is typically restricted airflow or inadequate ventilation around the cooktop. Induction and electric cooktops rely on sufficient clearance and airflow to dissipate heat generated during cooking. Blocked vents, debris accumulation beneath or around the unit, or installation in a recessed space without proper air circulation can all contribute to heat retention that pushes the radiator temperature beyond safe limits.

Additional causes can include a malfunctioning temperature sensor that reports inaccurate readings, a defective cooling fan that fails to move air through the unit, or extended operation at maximum power levels that generates more heat than the system can effectively manage. The first diagnostic step is to disconnect the cooktop from power completely and allow it to cool down before attempting any further inspection or restart. If the error persists after cooling and reconnecting power, deeper component-level diagnosis is required.

Source: manufacturer service documentation.

Common causes of c3

  1. 01

    Blocked or restricted ventilation

    Wiring / connection

    Debris, grease buildup, or improper installation clearance can block the airflow needed to keep the radiator cool. Inspect all vents and the underside of the cooktop for obstructions.

  2. 02

    Cooling fan failure

    Part replacement

    Many Thermador cooktops use an internal cooling fan to manage radiator temperature. If this fan has failed or is not spinning freely, heat will accumulate rapidly during use.

  3. 03

    Faulty temperature sensor

    Part replacement

    A defective or degraded radiator temperature sensor may trigger a false C3 error even when actual temperatures are within range. This typically requires testing the sensor for accurate resistance and response values.

  4. 04

    Extended high-power operation

    Wiring / connection

    Running multiple cooking zones at maximum power for prolonged periods can generate more heat than the radiator dissipation system can handle, especially in warmer ambient conditions.

  5. 05

    Internal wiring or component fault

    Part replacement

    Damaged wiring connections to the radiator or a failing heating element can cause localized overheating that triggers the C3 shutdown. Visual inspection of wiring harnesses near the radiator is recommended.

See the test procedure for each cause

Frequently asked questions about c3

What does c3 mean on a Thermador cooktop?
The C3 code on a Thermador cooktop signals a radiator temperature failure, meaning the cooktop has detected excessive heat at the internal radiator and shut down as a protective measure. The control system monitors radiator temperature during operation and triggers this error when that temperature exceeds safe limits. It is a safety feature designed to protect internal components from heat damage. Disconnecting the unit from power and allowing it to cool completely is the required first step.
Will resetting my Thermador cooktop clear the C3 error?
Disconnecting the cooktop from the power grid and allowing it to cool down fully can clear a C3 error if the cause was a temporary overheating event such as restricted ventilation or prolonged high-power use. However, if the underlying cause is a failed cooling fan, defective temperature sensor, or other component fault, the error will return after the unit warms up again during normal use. A reset without addressing the root cause is only a temporary measure.
Is it safe to keep using my cooktop when the C3 error appears?
No, you should stop using the cooktop immediately when C3 appears. The error indicates that the radiator has reached an unsafe temperature level, and continued operation could cause damage to internal components or create a safety hazard. The cooktop's automatic shutdown is a protective response that should be respected. Do not attempt to bypass or ignore this error code.
How do I fix a C3 error on a Thermador cooktop?
Start by disconnecting the cooktop from power and letting it cool completely, then inspect all ventilation openings for blockages or debris and ensure the unit has proper installation clearance. If the error returns after cooling and cleaning, the cooling fan or temperature sensor may need to be tested and potentially replaced. Persistent C3 errors that return quickly after restart typically require hands-on component-level diagnosis by a qualified technician.
How much does it cost to repair a Thermador cooktop showing a C3 error?
Repair costs depend heavily on the root cause. If the fix involves clearing a ventilation blockage, there may be no parts cost beyond a service call fee, which can range from roughly $75 to $150. If a cooling fan or temperature sensor needs replacement, total parts and labor costs can range from approximately $150 to $400 or more depending on the specific model and the rates of the technician. Complex internal faults or wiring issues may push costs higher.

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