What Does Error Code F21 Mean on a Bosch Washing Machine?

Bosch Updated 8 April 2026
Quick Fix

Power cycle the machine by switching it off at the wall, waiting 5 minutes, then switching it back on and restarting the programme — this clears temporary motor control errors and restores normal operation in many cases (takes about 5 minutes).

Fault description

Error code F21 is Bosch's way of telling you that something has gone wrong with the washing machine's drive motor system. The motor is responsible for rotating the drum during washing, rinsing, and spinning cycles, so when a fault is detected here, the machine will typically stop mid-cycle or refuse to start a new one altogether.

When F21 appears, the control board has received a signal — either from the motor itself or from the motor control module — that falls outside expected parameters. This could be anything from a brief electrical glitch to a more serious mechanical or electronic failure.

Before assuming the worst, it is worth working through a few straightforward checks. A significant number of F21 errors are caused by temporary faults that clear themselves once the machine is reset, or by issues with the motor brushes or wiring that a careful homeowner can inspect safely.

Causes

  • Temporary motor control glitch — The motor control electronics can occasionally produce a false fault signal due to a power surge or brief interruption. A simple reset often clears this without any physical fault being present.
  • Worn or depleted motor brushes — Many Bosch washing machine motors use carbon brushes to transfer current to the rotating armature. Over time these brushes wear down, causing intermittent or complete loss of motor function and triggering F21.
  • Faulty motor control module (MCU) — The motor control unit regulates power delivery to the motor. If this module develops a fault — due to age, heat damage, or a power spike — it can misread motor performance and generate an F21 error.
  • Damaged or loose motor wiring — The wiring harness connecting the motor to the control board can become loose, chafed, or corroded over time, particularly with the vibration of regular use. A poor connection here will cause the motor to behave erratically or not at all.
  • Seized or obstructed drum bearing — If the drum bearings have worn out or seized, the motor has to work much harder to turn the drum and may overheat or stall. The control board detects this abnormal load and raises the F21 fault.
  • Failed drive motor — In some cases the motor itself has reached the end of its service life or has suffered internal damage such as a burnt winding. This is less common but does occur on older machines or those used very heavily.

Step-by-Step Fix

  1. 1

    Reset the machine

    Turn the washing machine off at the wall socket and leave it unplugged for at least 5 minutes. This allows the control board to fully discharge and clear any stored fault state. Plug it back in, select a short programme, and observe whether F21 returns.

  2. 2

    Check the drum for obstructions

    Open the door and try turning the drum by hand. It should rotate smoothly with only light resistance. If it feels stiff, grinds, or will not turn at all, there may be a foreign object trapped between the drum and the tub, or the bearings may be failing.

  3. 3

    Inspect the motor wiring connections

    Switch off and unplug the machine, then carefully pull it away from the wall. Remove the back panel (usually held by two or three screws). Locate the motor at the base of the machine and check that all wiring connectors are firmly seated. Gently press each connector home and look for any visibly burnt, frayed, or corroded wires.

  4. 4

    Examine the carbon brushes

    With the back panel still removed, locate the motor brushes — they sit in plastic or metal holders on either side of the motor body and can usually be removed by unscrewing or unclipping them. A new brush is typically around 18–20 mm long; if yours are worn down to 5 mm or less, they need replacing. Replacement brushes are an inexpensive and straightforward DIY repair.

  5. 5

    Listen and observe during a test cycle

    After reassembling, run a short cotton cycle and listen carefully. A healthy motor runs with a steady hum. Loud buzzing, intermittent cutting out, or a burning smell all point to a motor or motor control issue that needs further investigation or professional attention.

  6. 6

    Check for error code recurrence

    If F21 returns after completing the steps above, note exactly when in the cycle it appears — during agitation, spin, or immediately on start-up. This information is very useful for a service technician and can help narrow down whether the fault lies with the motor itself or the motor control module.

Affected models

When to call a service technician

If the drum will not turn by hand, if you can smell burning from the motor area, or if F21 returns immediately after every reset attempt, these are signs that the fault is beyond basic DIY repair. A failed motor control module or a burnt-out motor winding requires specialist diagnostic equipment and safe handling of high-voltage components.

You should also call a service technician if you have replaced the motor brushes and the error persists, or if you notice any scorching or melted plastic around the motor or its wiring. Continuing to run the machine in this condition risks further damage to the control board and could create a safety hazard.

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Frequently Asked Questions

Can I still use my Bosch washing machine with an F21 error?

It is not advisable to keep running the machine once F21 appears. The error indicates the motor is not operating correctly, and continuing to use it could cause further damage to the motor, the control board, or both. Try the reset first, and if the fault clears and the machine completes a full cycle without issue, it is safe to continue using it while monitoring for recurrence.

How much does it cost to fix a Bosch F21 motor fault?

If the fix is simply replacing the carbon brushes, parts typically cost between £10 and £20 and the job is straightforward for a confident DIYer. A motor control module replacement will usually cost £60–£120 for the part alone, plus labour if fitted by a service technician. A full motor replacement is the most expensive outcome, with parts and labour potentially reaching £150–£300 depending on the model.

How do I know if it is the brushes or the motor that has failed?

Worn brushes usually cause the drum to turn slowly or intermittently before stopping, and the machine may work fine on some cycles but not others. A completely failed motor will typically mean the drum does not move at all from the start of the cycle. Inspecting the brushes visually is the quickest way to rule them out before suspecting the motor itself.

Why does F21 appear mid-cycle rather than at the start?

The motor works hardest during the spin cycle when it needs to reach high speeds. If the motor or its brushes are partially worn, they may cope with the slower agitation phase but fail under the higher load of spinning. An F21 that appears consistently at the same point in the cycle is a strong clue that the motor is struggling under load rather than having a wiring or control board issue.

Is F21 the same fault on all Bosch washing machine models?

The F21 code consistently refers to a motor fault across the Bosch washing machine range, though the exact component at fault can vary between models. Some older models use brush motors while newer ones use brushless inverter motors, which changes which parts are most likely to fail. Always check your specific model's service documentation or consult a service technician if you are unsure which motor type your machine uses.