d. Brush Treatment.
(1) General. New brushes must be properly
a. General. The starter-generator serves the dual
s e a t e d on the commutator before making the
purpose of starting the engine and of providing the
generator performance test. If the brushes have
output voltage by being driven by the engine during
been replaced they should be sanded and run-in to
normal operation. The starter-generator is mounted
properly seat them on the commutator before ap-
alongside the engine and is coupled to the engine by
plying a load to the generator. Failure to properly
a sheave and belt arrangement.
seat the brushes will result in excessive sparking,
b. Brush Replacement.
thus causing premature burning and pitting on the
(1) Remove the brush cover band assembly
commutator.
from the starter generator.
(2) Preliminary Brush Seating.
(2) Remove the screws and lift out the six
brushes. Replace old brushes with new brushes.
(a) Using a stiff wire hook raise each brush
spring and lift the brush away from the commutator
(3) Reinstall the brush cover band assembly on
far enough to permit a strip of 5/0 sandpaper to
the starter-generator.
slip under the brush. The sandpaper strip must be
c. Flashing the Starter-Generator Fields. If the
slightly wider than the combined width of the two
starter-generator voltage does not build up properly
brushes and located with sand side out. Cut the
due to loss of residual magnetism in the shunt field
sandpaper so that, when tight against the com-
circuit, flash the field as follows:
mutator, the two ends of the strip will lack ap-
(1) Connect the positive terminal of a 12-volt
proximately 1/32 inch of meeting. Secure the ends
battery through an SPST (single-pole, single-throw)
of the sandpaper with a small piece of adhesive tape.
knife switch to terminal A on the starter generator.
(b) Lower all brushes in place carefully
CAUTION
against the sandpaper making certain the brush
Always use a knife switch when flashing the
springs are properly positioned on the brushes.
field. Opening the circuit at the starter
(c) Rotate the armature slowly by hand in the
generator or battery terminals can result in
normal direction of rotation (clockwise when viewed
severe damage to the terminals or explosion
from air inlet end) until the brush contour matches
of the battery.
the cylindrical surface of the commutator. A brush
should be raised and inspected occasionally so that
the progress of the seating operation can be ob-
(2) Connect the negative terminal of the battery
served and the removal of unnecessary material
to terminal E on the starter generator.
avoided.
(3) Apply battery current to the shunt field for 5
seconds by closing the knife switch.
(d) Raise the brushes, remove the sandpaper
strip and carefully release the brushes against the
(4) Repeat the operation several times to be sure
commutator.
that the field is properly flashed.
Section XII. EXHAUST SYSTEM
2-39. Muffler and
Weather Cap
provided with a weather cap to keep moisture out of
the system.