Armature Check; Field Coils Check; Brush Holders Check; Gear And Pinion Housing Check/Bendix Drive Check - Piper PA-44-180 SEMINOLE Maintenance Manual

ARMATURE.
1. Check the commutator for uneven wear, excessive glazing or evidence of excessive arcing. If only slightly
dirty, glazed or discolored, the commutator can be cleaned with 00 or 000 sandpaper. If the commutator is
rough or worn, it should be turned in a lathe. Refer to Figure 80-2. The armature shaft should be inspected
for rough bearing surfaces and rough or damaged splines.
2. To test the armature for grounds, a set of test probes connected in series with a 110 volt light should be used.
Touch one probe to the commutator segment and the other to the armature core. If the test lamp lights, the
armature is grounded and should be replaced.
3. To test for shorted armature coils, a growler is used. Refer to Figure 80-3. The armature is placed on the
growler and slowly rotated by hand while a steel strip is held over the core so that it passes over each
armature core slot. If a coil is shorted, the steel strip will vibrate.
4. A quick check for opens can be made by inspecting the trailing edge (in direction of rotation) of the
commutator segments for excessive discoloration. This condition indicates an open circuit.
FIELD COILS. (See Figure 80-4.)
1. Check the field coils for grounds by placing one test probe on the frame and the other on the starter
terminal. Be sure the brushes are not accidently touching the frame. If the lamp lights, the fields are
grounded. Repair or replace.
2. Inspect all connections to make sure they are clean and tight and inspect insulation for deterioration.
BRUSH HOLDERS.
1. To test brush holders, touch one test probe to the brush plate and the other to each brush holder.
2. The test lamp should light when the grounded brush holders are touched and should not light when the
insulated brush holders are touched.
GEAR AND PINION HOUSING.
Inspect the housing for cracks and bearings for excessive wear. Remove rust, paint or grease from mounting
surfaces.
BENDIX DRIVE.
The Bendix Drive should be wiped clean with a dry cloth. The pinion should turn smoothly in one direction
and should lock in the other direction. Replace drive if it fails to check as above or if the pinion teeth are
excessively worn or damaged.
PIPER AIRCRAFT
PA - 4 4 - 1 8 0 / 1 8 0 T
AIRPLANE MAINTENANCE MANUAL
3I18
8 0 - 1 0 - 1 0
Page 80-06
Revised: May 15, 1989