What to check yourself
Step 1. Take half the laundry out
An overloaded drum, especially one holding a soaked duvet, can be heavy enough that the motor cannot bring it up to speed. The board reads that as a drive fault. Redistribute what is left evenly and try a short cycle.
Step 2. Turn the drum by hand
With the machine unplugged, reach in and spin the drum. It should turn freely with a light rumble. If it grinds, catches or will not move, something is jammed between the drum and the tub, often an underwire or a coin that has worked through the seal.
Unplug at the wall first. A drum that starts turning under power with a hand inside it is a serious injury.
Step 3. Listen for what happens when it tries
A motor that hums but does not turn, and a motor that turns in bursts then stops, point at different failures. Worth noting before you call anyone, because it is the first thing you will be asked.
What a technician will look at
Described so you know what you are paying for, not as steps to repeat.
Motor carbon brushes
On Bosch models with a brushed motor, worn carbon brushes are the classic cause of F21, and they are a wear item rather than a breakage: they simply run out after years of use. Newer machines with a direct drive motor have no brushes at all, so this does not apply to them.
Motor or control board
If the brushes are fine, the fault is in the motor itself, the tachometer that reports its speed, or the drive circuit on the control board. Telling these apart needs meter readings on a live machine.
When to call a technician
Straight away, if there is any burning smell, any grinding, or if the drum will not turn by hand. Otherwise, after you have ruled out an overloaded drum. This is not a fault to work through by swapping parts: the difference between a brush set and a control board is roughly five times the price.
What the repair costs
| Repair | Part only | Fitted by a technician |
|---|---|---|
| Motor carbon brush replacement | - | $100 to $200 |
| Motor replacement | - | $250 to $700 |
A new machine of the same class runs $500 to $1,500. Once a quote passes about a third of that on an older appliance, the repair stops making sense.
Codes people confuse this with
Questions people ask
- Is F21 worth repairing?
- If it turns out to be brushes, yes, easily: a hundred to two hundred dollars against five hundred and up for a new machine. If it is the motor or the board on a machine over about eight years old, the sums stop working, and an honest technician will tell you so.
- Can I replace the carbon brushes myself?
- Physically it is not a hard job on most models. But it means getting to the motor, working on a live circuit, and knowing whether your machine even has brushes. If you are not sure which type of motor you have, that answer alone is worth the call-out.
Which machines this applies to
Applies to
Bosch front loaders with brushed motors, common on machines built before the shift to direct drive. Related drive faults appear as F42, F43 and F44 on some European models.
Last checked
2026-08-03