O P E R A T O R S S T A T I O N
I N D I V I D U A L C I R C U I T D E S C R I P T I ON
S Y S T E M S O P E R A T I ON
S T A R T E R M O T O R A N D S O L E N O ID
3. Starter solenoid. 4. Starter motor.
D I S C O N N E C T
S W I T C H
5. Disconnect switch.
The starter solenoid is a solenoid switch that does two basic operations:
a. It closes the high current starter motor circuit with a low current start
switch and relay circuit.
b. It engages the starter motor pinion with the ring gear.
The solenoid switch is made of an electromagnet with two sets of windings
(pull-in coil and hold-in coil) around a hollow cylinder. There is a plunger (core)
with a spring load on it, inside the cylinder that can move forward and back-
ward. When current is sent through the windings, a magnetic field is made that
pulls the plunger forward in the cylinder.
When current is first sent to the solenoid from the start relay, it goes two
different ways. Part of the current goes through the hold-in windings to ground;
the rest of the current goes through the pull-in windings and then through the
starter motor windings to ground.