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Error code reference

Thermador Range Error Code d:18

WFMC motor control

Thermador codesThermador range codes

WFMC motor control: Peak voltage too high (faulty motor control).

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What d:18 means on a Thermador range

Error code d:18 on a Thermador range indicates that the WFMC (Washing/Fan Motor Control) motor control module has detected a peak voltage condition that exceeds acceptable operating thresholds. This fault is classified as an internal motor control fault, meaning the control board itself is registering an overvoltage event at the motor drive circuit. The motor control module monitors voltage levels supplied to the motor continuously, and when the peak voltage surpasses the designed tolerance, this code is triggered to protect the motor and associated circuitry from damage.

The most likely root cause of a d:18 fault is a faulty motor control board or module. Overvoltage conditions at the motor control level can stem from failures within the control module's internal voltage regulation components, such as capacitors, transistors, or rectifier circuits breaking down and allowing unregulated voltage spikes to reach the motor drive output. Incoming power supply irregularities, such as line voltage running significantly above nominal levels, can also stress the motor control circuitry and contribute to peak voltage faults.

Diagnosing this error typically requires measuring the incoming supply voltage at the terminal block to confirm it falls within the appliance's rated input range. If supply voltage is normal and stable, the motor control module itself is the primary suspect and will likely require replacement. Given that the fault meaning explicitly identifies the motor control as faulty, repair in most cases involves replacing the motor control board rather than a wiring or motor issue.

Source: manufacturer service documentation.

Common causes of d:18

  1. 01

    Faulty motor control module

    Part replacement

    The motor control board itself is the most common cause, as internal component failures such as failed capacitors or transistors can cause the board to generate or misread peak voltage conditions. Replacement of the module is typically required.

  2. 02

    High or unstable incoming line voltage

    Wiring / connection

    If the household supply voltage is running above the rated input level, the motor control circuitry can be exposed to excessive peak voltages. Measuring voltage at the terminal block with a multimeter will confirm or rule out this cause.

  3. 03

    Wiring fault or loose connection at motor control

    Wiring / connection

    Damaged, shorted, or loose wiring between the power supply and the motor control module can create voltage irregularities that trigger a peak voltage fault. Inspect all connectors and harnesses leading to the motor control board.

  4. 04

    Motor winding short or failure

    Part replacement

    A shorted motor winding can cause the motor control board to register abnormal voltage feedback, potentially triggering the peak voltage fault. Testing motor winding resistance can help identify this condition.

See the test procedure for each cause

Frequently asked questions about d:18

What does d:18 mean on a Thermador range?
The d:18 code on a Thermador range indicates that the WFMC motor control module has detected a peak voltage level that is too high. This is an internal motor control fault designed to protect the motor and drive electronics from overvoltage damage. The error points directly to the motor control module as the likely faulty component.
Can I fix a d:18 error on my Thermador range myself?
Some basic checks, such as verifying that incoming line voltage is within the normal range, can be performed by a knowledgeable DIYer with a multimeter. However, if the motor control module itself is faulty, replacement involves working with high-voltage components and internal circuitry, which is best handled by a qualified appliance technician. Attempting motor control board replacement without proper training carries a real safety risk.
Is it safe to keep using my Thermador range when d:18 is displayed?
It is not recommended to continue operating the range while this fault is active. The d:18 code indicates a motor control overvoltage condition, and continuing to run the appliance could cause further damage to the motor control board or connected components. Stop using the range and have it inspected before resuming normal operation.
Will resetting my Thermador range clear the d:18 error code?
A power cycle reset, such as disconnecting the range from power for several minutes and then restoring it, may temporarily clear the display, but the fault will return if the underlying cause has not been addressed. Because d:18 identifies a hardware-level fault in the motor control module, the error is unlikely to resolve permanently without repairing or replacing the faulty component.
How much does it cost to repair a Thermador range showing a d:18 error?
Repair costs will vary depending on the specific motor control module part cost and local labor rates, but motor control board replacements on Thermador ranges typically range from around $200 to $600 or more, including parts and labor. If the incoming line voltage is the cause, no parts may be required and cost would be limited to a service call. Getting a diagnostic visit from a certified technician will provide a more accurate estimate for your specific unit.

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