Taylor-Dunn AN 171 Operation, T Roubleshooting And Replacement Parts Manual Download

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Motor Service

Motor
Page 4

5. Inspect the commutator for burn marks.

• Burn marks and/or raised commutator segments

90 or 180 degrees apart is evidence of a shorted

armature. A tool called a growler is required to

reliably test for a shorted armature.

6. Inspect the commutator for raised segments.

Raised segments could be a result of a stalled

motor or shorted armature. A tool called a growler

is required to reliably test for a shorted armature.
• If the armature is not shorted then the raised

segments can be removed by machining the

commutator. Do not machine the commutator

past the minimum diameter specified in

Service Limits

section. Refer to

Repair

Commutator

section for information regarding

machining the commutator.

7. Visually inspect the armature windings for burnt

insulation. Burnt insulation is a direct result of

motor overheating and could lead to a shorted

armature.
• If the insulation is cracked or burnt, then it is

recommend that the armature or motor be

replaced.

NOTE: If the armature has been burnt then there is a

good possibility that the field windings may
also be burnt. Symptoms indicating a shorted
field include high motor current, lack of power
and possibly excessive speed.

8. Using a growler, test the armature for shorts.

• If the armature is shorted, then we recommend

that the armature or motor be replaced.

9. Using the continuity function of digital multi meter,

check the continuity around the entire commutator

by placing one test lead against one of the

commutator segments and the other test lead

against all of the other segments one at a time.

There should be continuity around the entire

commutator. If any segment indicates an open

circuit, then the motor must be replaced.

10. Using the continuity function of digital multi meter,

check the continuity from any one of the

commutator segments and the armature frame. If

it is not an open circuit, then the armature is

shorted and the motor must be replaced.

11. Rotate the motor bearing(s) by hand.

• The bearing should not ‘freewheel’ but should

come to a smooth stop when rapidly spun by

hand. If the bearing freewheels, then grease is

no longer present in the bearing and it must be

replaced. Refer to

Replacing the Bearings

section for information regarding replacing the

armature bearings.

• Feel for any roughness when the bearing is

rotated. If any roughness or grinding is noticed

then the bearing must be replaced. Refer to

Replacing the Bearings

section for

information regarding replacing the armature

bearings.

Assembly

NOTE: If this is an enclosed motor on a vehicle with

a Power Traction primary reduction, then it
is recommended to replace the armature
shaft seal any time the motor is
disassembled.

1. Push the motor brushes just far enough out of the

brush holder so that the brush springs hold them

in place away from the commutator. See the

illustration to the right.

2. Install the rear motor housing to the stator housing.
3. Lightly grease the outside diameter of the armature

bearings.

4. Insert the armature through the stator housing and

seat the bearing into the rear housing.

5. If equipped with armature retaining screws, install

and tighten them at this time.

6. If this is an enclosed motor, lightly grease the

armature shaft seal and install the front motor

housing.

NOTE: If the vehicle is equipped with a belt type

primary reduction then the spring on the
motor seal should be removed. Failure to
remove the spring may result in a high pitched
squeal from the seal.

7. Push the motor brushes into the brush holder until

the brush spring snaps into place. Be certain that

the spring does not rest up against the brush wire.

See the illustrations below.

Typical burn mark on a shorted armature