bosch fault code f21?

F21 relates to a motor or control board fault.
However, it is also caused by spikes in the mains and can be spurious.

If you have replaced the motor brushes,then the machine will need resetting,.
 
To reset it.
Turn the appliance knob to the off or reset position, 12 o'clock.
Turn the knob to the 6 o'clock position.
Press and hold the spin button.
Whilst holding it, turn the knob to the 7 o'clock position.
Continue holding the spin button for about 5 seconds.
Release the button.
Turn the knob to off.
When your turn it back on it should have cleared the error code.

paul
April 2012