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Starter motor

Starter motor


The starter motor has permanent magnets to reduce strain on the battery.

A planetary gear increases the starting torque.

The starter motor circuit consists of tow sub-circuits:


• working circuit

• operating circuit


Working circuit


The working circuit goes from the battery's positive terminal to terminal 30 on the starter motor.

Operating circuit


The operating circuit goes from the battery's positive terminal to the ignition switch and on to the starting relay, and via the starting relay to terminal 50 on the starter motor, which is the operating current connection on the solenoid.

On cars with automatic transmission, the gear selector lever must be in position P or N if the start relay coil is to receive a current.

The starting relay actuating coil is grounded via the TWICE control module when it has received the ready signal from the immobilizer unit.

Warning

Nothing may be connected to the circuit between the generator and the battery. Spikes of up to 100V can occur.


Operation

When the correct ignition key is put in the ignition, the transponder sends a code to TWICE, which grounds the starting relay actuating coil.

As the ignition is turned to start position, the starting relay operates and the operating circuit to the solenoid terminal 50 closes. The solenoid engages the pinion with the ring gear on the engine's flywheel and closes a switch so that the starter motor commutator is supplied with power via the slip brushes from terminal 30.

Once the engine is started and the engine speed exceeds the starter motor rpm, the pinion is disengaged from its shaft via a free wheel, preventing the starter motor from overrevving. Releasing the ignition key breaks the starting circuit and also the operating circuit to the solenoid, whereby a spring returns the pinion to its rest position.