The dc generator requires periodic cleaning,
lubrication, inspection of brushes and commutator,
and testing of brush spring tension. In addition, the
electrical connections need attention to ensure clean
metal-to-metal contact and tightness.
Some generators have hinged cap oilers. Lubricate
these with a few drops of medium weight oil at each
maintenance cycle. Do not overlubricate, because as
excessive amount of oil can get on the commutator and
prevent the brushes from functioning properly.
Visually and manually inspect the condition of all
cables, clamps, wiring, and terminal connections. See
that the generator drive pulley is tight on the shaft and
that the belt is in good condition and adjusted properly.
Also, ensure that the generator is securely mounted and
has a good ground.
Remove the cover band, on generator so equipped,
and inspect the inner surface of the generator cover
band for tiny globules of solder. If any solder is found,
the generator is producing excessive current and has
melted the solder used in connecting the armature
wires to the commutator bars. This condition requires
removal of the generator to repair or replace the
If no solder is found, inspect the commutator,
brushes, and electrical connections. If the commutator
is dirty or slightly rough, using 00 sandpaper can
smooth it. NEVER use emery cloth on the commutator.
Once the commutator has been sanded, blow
compressed air through the interior of the generator to
remove any excess dirt and brush particles. Lift the
Figure 2-14.Schematic wiring diagram of a typical dc charging circuit.
brushes in the brush holder to see that they are free to
operate and have sufficient tension to prevent arcing
and burning of the commutator and brushes. If brushes
are worn down to one half of their original length,
Most generators today are not equipped with cover
bands. They may have open slots over the commutator
or be sealed entirely. On those with open slots, the
commutator can be sanded through the slots, but brush
removal can only be accomplished by removing the
commutator end frame. On sealed units, maintenance
can only be performed after disassembly.
Generators are disassembled only when major
repairs are to be made (fig. 2-15). Other than cleaning
commutators and replacing worn-out brushes during
periodic maintenance, generators require very few
repairs during normal service life. However, if
neglected, generators will develop problems that
cannot be remedied in the field.
Before removing a generator suspected of being
faulty, you should check the battery, as discussed
earlier, and the generator output. Refer to the
manufacturers manual for correct generator output
specifications and proper testing procedures. If the
generator is operating properly and the battery, wiring,
and connections are in operating condition, a defective
voltage regulator is indicated in which, in most cases,
the regulator is removed and replaced. However, if the
generator is not producing the specified amperes at the
specified engine speed, then it must be removed from
the vehicle and either repaired or replaced.