Piper Arrow IV, Maintenance Manual

Page: 681 / 752

BRUSHES.
Check the brushes to see that they slide freely in their holders and make full contact on the commutator. If
worn to half their original length or less, they should be replaced.
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 a 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.
1. Check the field coils for grounds (refer to Figure 80-4) by placing one test probe on the frame and the
other on the starter terminal. Be sure the brushes are not accidentally 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 housings 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.
80-10-10
Page 80-07
December 1, 1978
3G18
PIPER AIRCRAFT
PA-28RT-201 / 201T
MAINTENANCE MANUAL