Power Train
Testing And Adjusting
Thermal Switch Tests
Open Circuits Test
Open Circuit Test
1.
Put the digital multimeter Function/Range Switch
on the 200 ohm resistance (½) scale.
2.
Put one test lead to each side of the thermal
switch harness.
3.
The resistance must be less than one ohm.
Ground Test
Ground Test
1.
Put the digital multimeter Function/Range Switch
on the 20M resistance (½) scale.
2.
Put one test lead to either of the plug prongs. The
other test lead must be grounded to the motor
housing.
There must be more than one megohm resistance.
Brush Life Estimate
1.
Before installation of new brushes, make an
inspection of the armature commutator, see
Armature Commutator Inspection in Testing and
Adjusting.
2.
Do the steps and procedures for New Brush
Installation in Testing and Adjusting.
3.
Make the initial (first) inspection of brush wear
between 250 smh and 500 smh. The reason for
this initial inspection is to see if the brush wear
rate is normal and not too fast. The measurement
will help make an estimate of the length of brush
life to be expected.
NOTE :
If there is an indication that brush wear is too
fast, see Troubleshooting, Problem: Sparks
at the commutator and/or rapid brush wear;
for probable causes of this problem.
4.
Inspect all brushes in the motors. Measure and
record each brush length (see Specification for
each new brush length and minimum brush length).
5.
Estimate expected brush life (hours). Use the
shortest measurement from Step 4 and the
following Sample Procedure:
Length of new brush ................45.8 mm (1.803 in.)
Minimum length of brush...............19 mm (0.75 in.)
New brush length [45.8 mm (1.803 in.)] - Minimum
brush length [19 mm(0.75 in.)] = Total amount of
usable brush wear [26.8 mm(1.055 in.)].
Length of shortest brush at 500 smh is 43.3 mm
(1.703 in.).
New brush length [45.8 mm (1.803 in.)] - Length of
shortest brush at 500 smh [43.3 mm (1.703 in.)] =
Amount of brush wear at 500 smh [2.5 mm (.10 in.)].
Amount of brush wear at 500 smh [2.5 mm (.10
in.)]
Ö
Total amount of usable brush wear [26.8
mm (1.055 in.)] = Portion of brush used at 500
smh (.1).
Service Meter Hours (smh) at brush wear
measurement (500 smh)
Ö
Portion of brush
used (.1) = Approximate total brush life of a new
brush (5000 smh).
Approximate total brush life of a new brush
(5000smh)ÐAmount of smh at brush life estimate
(500 smh) = Remainder of usable brush life
(4500 smh).
Tools Needed
Digital Multimeter Or Equivalent
1
20
