Daewoo G424 Gasoline Service Manual page 34

1
X
W
4
MTR BAT
MOTOR
Typical 12 Volt Starting Circuit
(1) Test point. (2) Test point. (3) Test Point. (4) Test Point. (5) Test Point. (X) Hold-in coil. (W) Pull-in coil.
Diagnosis Procedure
The following simplified procedure is intended to help
the serviceman determine if a starting motor needs to
be removed and replaced or repaired. It is not
intended to cover all possible problems and
conditions, but to serve only as a guide. The most
common 12 volt circuit is shown and discussed.
General Information
All starting systems are made up of four elements.
They are the ignition switch, start relay, the starting
motor solenoid and starting motor.
Start switches are relatively low current devices. They
are rated to switch approximately 5 to 20 amps.
Because the coil of a start relay [between test point (1)
and (2)] draws about 1 amp, the start switch can easily
turn on the start relay and have long life.
The switch contacts of a typical start relay are rated to
switch 30 amps. Because the solenoid requires 5 to 20
amps the start relay can easily switch this load.
The starting motor solenoid has two functions:
1. Engages the pinion with flywheel.
G424 Service Manual
2
WH
START
RELAP
3
RD/WH
STARTER
5
START
SWITC.H
2. Is a high current switch rated about 1000 amps that
actually turns on the starting motor.
The starting motor solenoid has two coils. Pull-in coil
(W) draws about 40 amps and hold-in coil (X) requires
about 5 amps. The instant the start relay closes, both
coils (W) and (X) receive power. Battery voltage is
applied to the high end of both coils, at test point (3)
which is the start (S) terminal. The low end of hold-in
coil (X) is permanently grounded to the ground post or
motor housing of the starting motor. Grounding for the
low end, test point (4), of pull-in coil (W) is momentary,
and takes place through the DC resistance of the
starting motor. As soon as magnetic force builds in
both coils, the pinion moves toward the flywheel ring
gear. The pinion will stop short of engagement of the
flywheel ring gear. Only then will the solenoid contacts
close to power the starting motor. This temporarily
removes the ground from pull-in coil (W), and puts
battery voltage on both ends of it while the starting
motor cranks. During this period, the pull-in coil is out
of the circuit. Cranking continues until power to the
solenoid is broken by releasing the ignition switch.
33
BATTERY
Starting System