What does the Bosch F21 error code mean?
F21 (sometimes shown as E21 on older models) indicates a motor speed fault. The drum is not rotating at the correct speed, or the motor’s tachometer (speed sensor) is sending unexpected readings to the control board. Often caused by an overloaded drum, worn brushes, or a faulty tachometer coil.
How to fix the Bosch F21 error code
- Check the load — an overloaded drum can trigger this. Remove half the laundry and retry.
- Run a spin-only cycle with an empty drum. If it spins fine, overloading was the cause.
- If the drum still won’t spin, check and replace carbon brushes as described in the E02 guide.
- If brushes are good, the tachometer coil (attached to the motor) may need testing with a multimeter — it should read 50–200 ohms.
- A faulty tachometer is usually replaced as part of the motor assembly.
Affiliate disclosure: This page contains affiliate links. We may earn a small commission if you buy through them, at no extra cost to you.