Armature; Field Coils; Brush Holders; Bendix Drive - Piper Dakota Maintenance Manual

ARMATURE

1. Check 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
commutator is rough or worn, it should be turned in a lathe. (Refer to figure 80-2.) Inspect armature
shaft for rough bearing surfaces and rough or damaged splines.
2. To test armature for grounds, use a set of test probes connected in series with a 110-volt light. Touch
one probe to a commutator segment and other to armature core. If test lamp lights, armature is
grounded and must be replaced.
3. Use a growler to test for shorted armature coils. (Refer to figure 80-3.) Place armature on growler and
slowly rotate by hand while a steel strip is held over core so that it passes over each armature core slot.
If a coil is shorted, steel strip will vibrate.
4. A quick check for open circuits is made by inspecting the trailing edge (in direction of rotation) of the
commutator segments for excessive discoloration.

FIELD COILS

1. Check field coils for grounds (refer to figure 80-4) by placing one test probe on frame and other on
starter terminal. Be sure brushes are not accidentally touching frame. If lamp lights, 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 brush plate and other to each brush holder.
2. The test lamp should light when grounded brush holders are touched and should not light when
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

Wipe Bendix Drive 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 pinion teeth are excessively worn or
damaged.
PIPER AIRCRAFT
PA-28-236
MAINTENANCE MANUAL
2L3
80 - 12 - 00
Page 80 - 07
Reissued: August 1, 1986