SPECIFICATIONS

Vehicle Systems Testing And Adjusting
Thermal Switch (Thermostat) Tests
Open Circuit Test
Open Circuit Test(Typical Example)
1. Put the digital multimeter Function/Range Switch
on the 200 ohm resistance (A) 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 (Typical Example)
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, inspect 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.
4. Inspect all brushes in the motors. Measure and
record each brush length. See Hydraulic Pump or
Steering Pump Motor in Specifications for new
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 (.75 in)
New brush length [45.8 mm(1.803 in)] - Minimum
brush length [19 mm (.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)] 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) Portion of brush used ( .1)
= Approximate total brush life of a new brush (5000 smh).
Approximate total brush life of a new brush (5000
smh) - Amount of smh at brush life estimate (500
smh) = Remainder of usable brush life (4500 smh).
6. The smh estimate of brush life can be used if the
machine is to work at the same rate (duty cycle),
the battery is not discharged too much or the
battery cells have not become damaged. If the
machine is made to work harder, the battery is
discharged too much, or the battery cells become
damaged, the motor temperature will get hot very
fast. This will cause rapid wear of the brushes.
7. It is important to check brush length and brush
condition at a specific time, such as during the
preventive maintenance check. If an inspection
shows that brush life will not extend to the next
preventive maintenance check, install new brushes.
Tools Needed
Digital Multimeter Or Equivalent 1
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