TM 5-3895-382-24
Starting Motor
Illustration 106
Starting circuit for 12 volt system. (typical example)
(1) Test point
(2) Test point
(3) Test point
(4) Test point
(5) Test point
(X) Hold-in coil
(W) Pull-in coil
Procedures For Diagnosis Of The
Starting Motor
The procedures for diagnosing the staring motor are intended
to help the serviceman determine if a starting motor needs to
be replaced or repaired. The procedures are not intended to
cover all possible problems and conditions. The procedures
serve only as a guide. The most common 12 volt circuit is
shown in Illustration 106.
General Information
All electrical starting systems have four elements:
Ignition switch
Start relay
Starting motor solenoid
Starting motor
Start switches have a capacity of 5 to 20 amperes. The coil of
a start relay draws about 1 ampere between test points (1) and
(2). The switch contacts of the start relay for the staring motor
are rated between 100 and 300 amperes. The start relay can
easily switch the load of 5 to 50 amperes for the staring motor
solenoid.
The staring motor solenoid is a switch with a capacity of about
1000 amperes. The staring motor solenoid has two functions:
The pinion gear is engaged with the ring gear of the
flywheel.
The starting motor is rotated.
The starting motor solenoid has two coils. Pull-in coil (W)
draws about 40 amperes. Hold-in coil (X) requires about 5
amperes.
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