put the armature in the growler and then plug it
into an AC source.take something like a
hacksaw blade and pass it back and forth
from left to right over the armature slots.
keep the saw blade horizontal with the shaft
and as close as possible to the armature.if the armature doesn't attract the blade, turn
the AC source off and turn the armature as
many slots as have not been touched on the
bottom by the growler. turn the AC source back on and repeat the
above procedure until the entire armature
has been rotated and tested. a short circuited coil will be indicated
by a strong pull on the saw blade at the
slot that the short circuited coil lies in.
since you don't know if the short circuit
is at the top or the bottom of the coil,
mark the slot and then turn the armature
to the right or left for as many slots
as one coil spans and make the test again.
if you get no pull, turn to the opposite
direction and make the test again. when the shorted coil is located, examine
the commutator bars where the coil is
connected.you are looking for metallic
particles between the bars or anything
else like that that would cause a short. if it isn't something simple like that,
your short could be caused by degraded
insulation --- coil turns touching each
other or one coil contacting another coil.
you can also use just a test lamp made
up of wires soldered to a low voltage lamp
in conjunction with your growler.
with the armature in the growler, make a bar
to bar test with the lamp.the lamp should
be the same brightness on all the bars.
to do this test, it's important that
the lamp stays in the same position
relative to the growler as you rotate
the armature moving from bar to bar. a short in this method will show a dim
or no light.
hope this helps
doug handran
: Years ago, in high school auto shop, I learned to use an armature growler.My memory fades as to the complete and exact procedure.I just purchased a used gowler to assist in rebuilding my model A starters and generators.I wonder if any of you could explain the procedure for me.Thanks.
: Steve | 
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