Starter Solenoid Test; Armature Open Circuit Test; Grounded Armature Test - Ford LRG-423 Service Manual

03-48
Auxiliary Systems
03-48
STARTER, PERMANENT MAGNET DIAGNOSIS ANDTESTING (Continued)
2. Disconnect starter from battery. Then, reduce
resistance of rheostat until voltmeter indicates
same reading as that obtained while starter was
running. The ammeter will indicate starter no-load
current draw. Refer to Specifications for a
comparative value.
3.
If current exceeds specification, check for rubbing
armature, bent shaft, binding bearings, or shorts
in armature, or brush assembly.
Armature Open Circuit Test
An open circuit armature may sometimes be detected
by examining the commutator for evidence of burning.
A burn spot on the commutator is caused by an arc
formed every time the commutator segment,
connected to the open circuit winding, passes under a
brush.
Grounded Armature Test
This test will determine if the winding insulation has
been damaged, permitting a conductor to touch the
frame or armature core. To determine if the armature
windings are grounded, check with a VOM as shown.
Infinite resistance indicates a normal condition.
Starter Solenoid Test
Make sure that the solenoid is isolated electrically from
the motor. Using a VOM, check for continuity between
" S" terminal and " M" terminal, and between " S"
terminal and ground (frame). If there is no continuity,
the wire is broken and the solenoid should be
replaced.
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