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Error code reference

Thermador Range Error Code FC

Communication error detected by display head; 2nd power/relay board not powered up (S/SM/SMW).

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Communication error detected by display head; 2nd power/relay board not powered up (S/SM/SMW).

First step from the service manual

Check cables and harnesses between main and 2nd power/relay boards; check connections to control head; if persists replace 2nd power/relay board then display head then main 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 FC means on a Thermador range

The FC error code on a Thermador range signals a communication failure detected by the display head, specifically indicating that the second power/relay board has not powered up properly. This code is relevant to Thermador S, SM, and SMW series ranges, which use a multi-board control architecture where a main power/relay board, a secondary power/relay board, and a display control head must all communicate in sequence during startup. When the display head does not receive an expected signal from the second power/relay board, it logs the FC fault and halts normal operation.

The communication path between these boards runs through a series of cables and wire harnesses. A loose connector, damaged wiring, or corroded terminal along this path can interrupt the signal before it ever reaches the display head, triggering the FC code even if the second power/relay board itself is functioning. Physical inspection of all harness connections between the main board, secondary board, and control head is the essential first diagnostic step.

If wiring and connections check out, the fault likely originates in a failed component. The second power/relay board is the most probable failed part, as it may not be receiving adequate power or may have an internal failure preventing it from initializing. If replacing the second power/relay board does not resolve the error, the display head should be replaced next, followed by the main power/relay board as a last resort. The sequential replacement order reflects the relative likelihood of failure for each component.

Source: manufacturer service documentation.

Common causes of FC

  1. 01

    Loose or disconnected wiring harness

    Wiring / connection

    A cable or connector between the main power/relay board, the second power/relay board, or the display head may have worked loose over time. Inspect all harness connections at each board for secure seating and signs of corrosion or heat damage.

  2. 02

    Failed second power/relay board

    Part replacement

    The secondary power/relay board may have an internal failure preventing it from powering up and communicating with the display head. This is the most likely component failure if wiring inspections come back clean.

  3. 03

    Damaged wiring harness

    Part replacement

    Physical damage to the cables running between the boards, such as chafing, pinching, or heat exposure, can break the communication circuit. Look for visible wire damage along the full length of each harness.

  4. 04

    Failed display head

    Part replacement

    The control display head itself may be generating the FC fault due to an internal failure in its communication circuitry, even when the second power/relay board is operating correctly. This is diagnosed after ruling out wiring and the secondary board.

  5. 05

    Failed main power/relay board

    Part replacement

    In rare cases, the main power/relay board may not be supplying the correct power or signals needed for the second board to initialize. This is the last component to suspect and replace in the diagnostic sequence.

See the test procedure for each cause

Frequently asked questions about FC

What does FC mean on a Thermador range?
The FC code on a Thermador range indicates a communication error detected by the display head, specifically that the second power/relay board did not power up as expected. This applies to S, SM, and SMW series models that use multiple control boards working together. The fault disrupts normal communication between the control head and the board responsible for managing power to range components.
Can I fix the FC error code myself on a Thermador range?
Some causes of the FC code are accessible to a knowledgeable DIYer, particularly checking and reseating wiring harnesses and connectors between the control boards. However, if the fault persists after inspecting connections, replacing the second power/relay board, display head, or main board requires comfort working inside high-voltage appliances. If you are not experienced with appliance electronics, a qualified technician is the safer choice.
Is it safe to use my Thermador range while the FC error is active?
The FC error indicates a breakdown in communication between the control boards, which means the range may not respond to controls correctly or at all. Operating a range in this condition is not recommended, as the control system cannot reliably manage heating elements. The range should remain off until the fault is diagnosed and resolved.
Will resetting my Thermador range clear the FC error code?
Cycling power to the range by unplugging it or switching off the circuit breaker for a few minutes may temporarily clear the FC code if the fault was caused by a transient communication glitch. However, if the underlying cause is a loose connection or a failed board, the error will return when the range powers back up. A reset alone is not a repair.
How much does it cost to repair an FC error on a Thermador range?
Repair costs vary depending on which component has failed. Wiring harness repairs or connector reseating typically involve only a service call fee, which can range from around $80 to $150 or more depending on location. Replacing the second power/relay board or display head adds parts costs that can range from $150 to $400 or higher per board, plus labor. Replacing the main power/relay board is typically the most expensive scenario.

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