510 Section 5 Electrical and Electronic Systems Technology
Then, lever action of the drive yoke pushes the pin-
ion gear outward on its shaft. This causes pinion
gear engagement as the armature begins to spin.
When the motor is shut off, a spring moves the pin-
ion gear and pole shoe into the released position.
A starter-actuated solenoid has a plunger that
moves a shift lever to engage the pinion gear. The
solenoid is mounted on the side of the starter fi eld
frame. With this starter design, the solenoid com-
pletes the battery-to-starter circuit and also operates
the pinion gear. See Figure 30-15B.
12-Volt Neutral Safety Switch
A neutral safety switch prevents the engine from
cranking unless the shift selector is in neutral or park.
It keeps the starting system from working when the
transmission is in gear. The switch provides a safety
feature to prevent the car from starting while in gear.
Cars with automatic transmissions commonly
have a neutral safety switch. The switch may be
mounted on the shift lever mechanism or on the
transmission.
Neutral Safety Switch Operation
The neutral safety switch is wired into the cir-
cuit going to the 12-volt starter solenoid. When the
transmission is in drive or reverse, the neutral safety
switch is open (disconnected). This prevents current
from activating the solenoid and starter when the
start switch is turned to start.
With the transmission in park or neutral, the neu-
tral safety switch is closed (connected). Current can
fl ow to the 12-volt starter when the start switch is
turned.
Tech Tip
In most late-model cars, the brake light switch
is wired into the same control circuit as the
neutral safety switch. You must have the
transmission in park (or neutral) and press the
brake pedal for the starting motor to energize.
12-Volt Starter Relay
A relay is a device that opens or closes one circuit
by responding to an electrical signal from another
section of a circuit. Most modern starting systems
use a relay between the ignition switch (start button)
or the ECM and the 12-volt starter solenoid.
A starter relay uses a small current fl ow from the
start switch or ECM to control a slightly larger cur-
rent fl ow to the starter solenoid. This further reduces
the load on the ignition key switch. A 12-volt starter
relay circuit is shown in Figure 30-16.
Starter Relay Operation
When the ignition switch is turned to start, current
fl ows into the relay. This closes the relay contacts.
The contacts complete the circuit to the solenoid
windings and the starting system operates.
Start/
ignition
switch
Motor
frame
Shift
collar
Pinion
compression
spring
Clutch
Engine
flywheel
Plunger Coil
Solenoid
Solenoid
switch
contacts
Shift
lever
Pinion gear
Neutral safety
switch (automatic
transmission only)
To battery
Battery
Starter relay
Figure 30-16. Study the complete manual starting system circuit. This circuit has a 12-volt starter relay. The relay further decreases
the amount of current fl owing through the ignition start switch. Also note how the relay winding is wired to the neutral safety switch.
(Chrysler)