Starting System: Description and Operation

Fig. 1 Bosch Starter Motor:

Bosch starters are either direct drive or gear reduction type starters. Bosch direct drive starters incorporate an overrunning clutch type starter drive. A solenoid switch is mounted on the starter motor.
Bosch gear reduction starters use six permanent magnets in place of conventional, wound field magnets, to save weight, eliminate field winding to case shorts, and improve cold start performance. The gear reduction system uses a planetary gear train to transmit armature rotation to the pinion shaft. A solenoid switch is mounted on the starter motor drive end shield.