What this error means
The F21 error code on your Bosch washing machine means the machine has detected that the motor is not rotating in the correct direction or at the correct speed — a motor rotation fault.
The F21 error code indicates that the control board has detected incorrect or absent motor rotation. During a wash cycle, the motor alternates between clockwise and anticlockwise rotation to agitate the laundry. The machine monitors the rotation pattern via the tachometer and through feedback from the motor control unit. If the rotation signal is absent, incorrect, or erratic, the machine stops and displays F21. Common causes include worn motor carbon brushes (on brush-motor models), a faulty motor tachometer, a fault with the motor control board, or in some cases an imbalanced load that is preventing the drum from turning freely. A power reset and load check should always be the first steps before assuming a component failure.
What you'll need first
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Step-by-step
Symptoms to look for
- F21 displayed on the control panel
- Drum not rotating or rotating in only one direction
- Machine stops during the wash agitation phase
- Machine fails to reach spin speed or stops during spin
- Unusual clicking or grinding sound when drum tries to start
Diagnostic steps
Unplug the machine from the wall socket and leave it for a minimum of 5 minutes. This resets the motor control unit and clears any temporary fault condition triggered by a momentary rotation anomaly. Plug back in, select a short programme, and observe.
Unplug the machine. Open the door and inspect the drum carefully — look and feel around the inside edges, particularly around the door seal lip and the drum paddles. Small hard objects such as coins, bra underwires, and bones from boned clothing can wedge between the drum and the machine body, preventing rotation. Wear thick rubber gloves when feeling around the edges as sharp objects can cause cuts.
With the machine still unplugged, reach inside and try rotating the drum by hand. It should turn with moderate resistance — think of turning a steering wheel one-handed. If the drum does not move at all, is extremely stiff in one direction, or makes grinding/scraping sounds, there is either a physical obstruction or a seized motor or bearing.
On older Bosch washing machines (typically pre-2012) the drive motor uses carbon brushes. Worn brushes are one of the most common causes of rotation faults including F21. To check: switch off and unplug the machine, remove the back panel, locate the motor (usually at the bottom of the machine), and inspect the brush holders on each side. The brushes should be clearly longer than the brush holder mouth. If they are flush with or shorter than the holder, they need replacing.
The tachometer is a small sensor (usually circular, about 3 cm in diameter) clipped onto the rear shaft of the motor. It detects the motor's rotation speed and direction. If the tacho has slipped out of position, is disconnected, or has failed, the machine will display F21 even with a healthy motor. An engineer can test it with a multimeter.
If F21 returns consistently after a power reset and with an empty drum that rotates freely by hand, the fault requires electrical testing of the motor, tachometer, motor control board, and associated wiring. Contact a qualified engineer and provide the full model number and a description of when F21 appears (at the start, during wash, during spin, etc.).
When to call an engineer
- F21 returns consistently after reset with an empty drum
- Drum does not rotate by hand (possible seized motor or bearing)
- Tachometer found to be disconnected, damaged, or out of position
- Motor brushes confirmed as worn below minimum length
- Motor control board fault found on electrical testing
Frequently asked questions
What does F21 mean on a Bosch washing machine?
Is F21 different from E21 on a Bosch washing machine?
Can I fix Bosch F21 myself?
Why does F21 appear on my Bosch washing machine during the spin cycle?
How do I clear F21 on my Bosch washing machine?
🎯 What is most likely causing your Bosch F21 error?
⚠️ Estimates based on common faults — not a guaranteed diagnosis. Always verify before ordering parts.
Parts you may need
Enter your model number to filter results to your exact machine
Usually found on a label inside the door frame or on the back panel of the machine.
| Part | Approx. UK Cost | Find it |
|---|---|---|
| Bosch Motor Carbon Brushes | £5 - £10 | 🛒 Amazon UK → |
| Bosch tachometer coil | £20 - £30 | 🛒 Amazon UK → |
ℹ️ Prices are approximate. Always check the part number matches your model before ordering. Not sure of your model number? Find out how to locate it here.