User Manual

58 SENR9977
Testing and Adjusting Section
When it is possible, make a test of the charging
unit and voltag
e regulator on the engine, and use
wiring and components that are a permanent part of
the system. Off-engine testing or bench testing will
giveatestoft
he charging unit and voltage regulator
operation. This testing will give an indication of
needed repair. After repairs are made, perform a test
in order to pr
ove that the units have been repaired to
the original condition of operation.
Alternator Regulator
The charging
rate of the alternator should be checked
when an alternator is charging the battery too much
or not charging the battery enough.
Alternator output should be 28 ± 1 volt on a 24 volt
system and 14 ± 0.5 volt on a 12 volt system. No
adjustment
can be made in order to change the rate
of charge on the alternator regulators. If the rate of
charge is not correct, a replacement of the regulator
is necessa
ry. For individual alternator output, refer to
Specification, “Alternator and Regulator”.
i01945632
Electric Starting Sys tem - Test
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. The switch contacts of the start
relay for the starting motor are rated between 100
and 300 amperes. The start relay can easily switch
the load of 5 to 50 amperes for the starting motor
solenoid.
Thestartingmotorsolenoidisaswitchwithacapacity
of about 1000 amperes. The starting motor solenoid
supplies power to the starter drive. The starting motor
solenoid also engages the pinion to the flywheel.
The starting motor solenoid has two coils. The
pull-in coil draws about 40 amperes. The hold-in coil
requires about 5 amperes.
When the magnetic force increases in both coils,
the pinion gear
moves toward the ring gear of the
flywheel. Then, the solenoid contacts close in order
to provide power to the starting motor. When the
solenoid cont
acts close, the ground is temporarily
removed from the pull-in coil. Battery voltage is
supplied on both ends of the pull-in coil while the
starting mot
or cranks. During this period, the pull-in
coil is out of the circuit.
Cranking of t
he engine continues until current to the
solenoid is stopped by releasing the ignition switch.
Power which i
s available during cranking varies
according to the temperature and condition of the
batteries. The following chart shows the voltages
which are ex
pected from a battery at the various
temperature ranges.
Table 9
Typical Voltage Of Electrical System During Cranking
At Various Ambient Temperatures
Temperature 12 Volt
System
24 Volt
System
−23 to −7°C
(−10 to 20°F)
6to8volts 12 to 16 volts
−7to10°C
(20 to 50°F)
7to9volts 14 to 18 volts
10 to 27°C
(50 to 80°F)
8to10volts 16 to 24 volts
The following table shows the maximum acceptable
loss of voltage in the battery circuit. The battery
circuit supplies high current to the starting motor.
The values in the table are for engines which have
service of 2000 hours or more.
Table 10
Maximum Acceptable Voltage Drop In The Starting
Motor Circuit During Cr anking
Circuit 12 Volt
System
24 Volt
System
Battery post “-” to
the starting motor
terminal “-”
0.7 volts 1.4 volts
Drop across the
disconnect switch
0.5 volts 1.0 volts
Battery post “+”
to the terminal of
the starting motor
solenoid “+”
0.5 volts 1.0 volts
Solenoid terminal
“Bat” to the solenoid
terminal “Mtr”
0.4 volts 0.8 volts