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Error code reference

Miele Washer Error Code F4099

Clock module fault; internal system clock fault or backup capacitor discharged (resets to 01.01.2003 if…

Miele codesMiele washer codes

Clock module fault; internal system clock fault or backup capacitor discharged (resets to 01.01.2003 if unpowered >6 weeks).

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What F4099 means on a Miele washer

The F4099 error code on a Miele washer indicates a fault within the clock module, specifically involving the machine's internal real-time clock (RTC) or its associated backup capacitor. The RTC is responsible for maintaining accurate timekeeping within the washer's control electronics, which is used for scheduling, logging operational data, and coordinating timed wash cycles. When the control board detects that the clock has lost synchronization or that the backup capacitor has discharged to a point where it can no longer sustain the clock during power outages, the F4099 code is triggered.

A key diagnostic indicator for this fault is the date to which the machine resets. If the washer has been without power for more than approximately six weeks and the RTC reverts to 01.01.2003 (January 1, 2003), this confirms that the backup capacitor is fully discharged or has failed entirely. The backup capacitor serves as a small energy reserve that keeps the clock running during brief power interruptions. Over time, electrolytic capacitors degrade and lose their ability to hold a charge, making this a common failure mode in older units.

The fault may also appear due to a broader clock module failure unrelated to the capacitor, such as a faulty crystal oscillator or corrupted clock circuitry on the main control board. In some cases, a simple power interruption or voltage fluctuation can cause a temporary clock fault that clears after restoring power and resetting the machine. Persistent faults following a reset typically point to a hardware failure requiring component-level repair or board replacement.

Source: manufacturer service documentation.

Common causes of F4099

  1. 01

    Discharged or failed backup capacitor

    Part replacement

    The backup capacitor that maintains the real-time clock during power loss has degraded and can no longer hold a charge. This is confirmed when the machine resets its date to 01.01.2003 after being unpowered for more than six weeks.

  2. 02

    Extended power outage or disconnection

    Wiring / connection

    If the washer was unplugged or lost mains power for more than approximately six weeks, even a functioning capacitor may have fully discharged. Restoring power and resetting the machine may resolve the fault temporarily if the capacitor is otherwise healthy.

  3. 03

    Clock module or RTC circuit failure

    Part replacement

    A fault within the real-time clock circuitry itself, such as a failed crystal oscillator or corrupted clock logic on the control board, can trigger F4099 independently of the capacitor. This fault will persist after resets and requires board-level diagnosis.

  4. 04

    Control board fault

    Part replacement

    Broader failure of the main control board can affect the clock module's operation and produce this error. If other error codes accompany F4099 or multiple functions are impaired, the control board should be inspected.

  5. 05

    Voltage fluctuation or power surge

    Wiring / connection

    A transient voltage spike or brief power interruption can temporarily corrupt the clock register. In these cases the fault may not recur after a reset and power cycle.

See the test procedure for each cause

Frequently asked questions about F4099

What does F4099 mean on a Miele washer?
F4099 indicates a clock module fault, meaning the washer's internal real-time clock has lost its time reference or stopped functioning correctly. This is often caused by a discharged backup capacitor that can no longer maintain the clock when the machine is unpowered. A clear sign of this issue is the machine reverting its date to 01.01.2003 after being without power for more than six weeks.
Can I fix F4099 myself or does it require a technician?
If the fault appeared after a long power outage, restoring power and performing a reset may clear it temporarily if the backup capacitor still has some capacity. However, a persistent F4099 fault typically requires replacement of the backup capacitor or the control board, which involves working with sensitive electronics. For component-level repair, a qualified appliance technician is recommended.
Is it safe to use my Miele washer while F4099 is displayed?
The F4099 fault relates specifically to the internal clock and timekeeping functions rather than core wash or safety systems. In many cases the washer will still complete cycles, but delayed-start or scheduled cycle features that rely on accurate timekeeping may not function correctly. It is advisable to address the fault promptly to avoid potential complications with cycle management.
Will resetting the washer clear the F4099 error code?
A power cycle or reset may temporarily clear the code if the fault was caused by a brief voltage fluctuation or a recoverable clock error. However, if the backup capacitor has degraded or the clock circuitry has failed, the error will return because the underlying hardware issue has not been resolved. A persistent F4099 after multiple resets points to a component failure requiring physical repair.
How much does it cost to repair a Miele washer with error code F4099?
Repair costs vary depending on the root cause. If only the backup capacitor needs replacement, costs are generally in the lower range for parts and labor, typically between $75 and $200 depending on your location and service rates. If the entire control board requires replacement, costs can range from $250 to $600 or more, as Miele control boards are precision components. Getting a diagnostic from a Miele-authorized technician will clarify exactly which parts are involved.

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